Glossary

Here are the connector terms both the Hobby and Professional / Industrial tracks use. Each one links to the page that goes deeper. Three warnings before the alphabet starts: "male/female" is ambiguous because housing gender and contact gender are separate; "plug" and "receptacle" change meaning between vendors; and marketplace names are much less trustworthy than drawings. Say exactly what you mean and check the mating diagram. If you're doing Week 1 of the 30-Day Plan, use this as a starting point, then rewrite 30 of these in your own words.

360° shield termination — bonding the cable shield circumferentially into the backshell/shell instead of through a pigtail wire; keeps shield impedance low across frequency. See EMI, shielding, and bonding.

AS39029 — the SAE specification (formerly M39029) for the removable crimp contacts used in MIL-DTL-38999 and related mil circulars. See Contact sizes and current.

Authorized / franchised distributor — a distributor selling under agreement with the manufacturer: factory traceability, manufacturer warranty, and PCN/EOL notices flow. The default channel for released hardware. See Lifecycle & Procurement.

Backshell — the rear accessory that provides strain relief, shield termination, sealing, and cable exit angle. Not optional. See Connector Anatomy.

Blind mate — mating a connector the operator can't see; needs lead-in, float, and pin-length stagger. See Mating sequence and blind mate.

Broker / independent distributor — a distributor operating outside manufacturer agreements; a legitimate channel for obsolete/allocated parts under counterfeit-avoidance controls, but traceability must be verified per lot. See Lifecycle & Procurement.

Bundle derating — reducing allowable per-contact current as more contacts are energized, because packed contacts heat each other. See How to read a derating curve.

Coding (M12) — the keyway geometry (A/B/D/X/S/T/K/L) that maps an M12 connector to its application class and prevents cross-mating. See M12 Deep Dive.

Connection type — wire-to-board (housing on wires, header on a PCB), wire-to-wire (two cable halves mate in-line), board-to-board (stacking/mezzanine), or panel/feedthrough. The first sorting question for any unknown connector. See the identification workflow.

Connector family / series — the manufacturer-defined system of housing + contacts + pitch + latch + tooling + mating part, controlled by a drawing. The unit of compatibility: parts interchange within a family, not between lookalikes. See The Big Idea.

Connector saver — a sacrificial adapter left on a high-cycle test port so mating wear lands on the cheap replaceable part. See RF orientation.

Contact / terminal — two names for the same part: the metal element crimped onto the wire and inserted into the housing. "Terminal" dominates kit and marketplace language; "contact" dominates datasheets. Family-specific either way. See Crimping.

Contact resistance — the milliohm-level resistance through a mated contact pair; rises with cycles and fretting, critical for low-level signals. See Reading Datasheets and Low-Level Signal Contacts.

Contact size — the numbered physical contact size (22D, 20, 16, 12, 8…); smaller number = larger contact = more current and larger wire. See Contact sizes and current.

COTS — commercial off-the-shelf; purchasable as a standard catalog item rather than qualified/QPL hardware. See Production reality.

Creepage / clearance — creepage is the shortest path along a surface between two conductors; clearance is the shortest through-air gap. Both drive voltage rating. See Electrical requirements.

Crimp — terminating a wire by compressing it into a contact barrel with a calibrated tool; the standard for rugged harnesses. See Termination types and, for the hobby-scale version, Crimping Without Losing Your Mind.

Current rating — a screening number tied to test conditions, never universal permission: the real limit depends on the exact contact, wire gauge, loaded positions, ambient temperature, and allowable temperature rise. See the derating-curve entry, Power vs Signal, and Selection Workflow §2.

Derating curve — the manufacturer plot of allowable current vs. loaded-contact count and temperature; the number you actually design to. See How to read a derating curve.

Dry circuit — a circuit whose voltage and current are too low to break down the films that grow on contact surfaces, so the contact must be reliable without electrical help — noble (gold-class) plating, adequate force, and wipe. Most measurement and low-voltage signal lines qualify. See Low-Level Signal Contacts.

Dust cap — the cover that protects an unmated connector from dirt, water, and pin damage; belongs on the BOM. See Connector Anatomy.

DWV / hi-pot — dielectric withstanding voltage; the survivable overvoltage test, not the continuous working voltage. See Reading Datasheets and the Qualification Plan Template.

EOL / last-time buy (LTB) — a manufacturer's discontinuance of a part, announced with final-order and final-ship dates; the decision point for a bridge buy, an approved alternate, or a redesign. See Lifecycle & Procurement.

First article inspection (FAI) — verifying that the first built unit(s) of a configuration match the complete drawing package before performance results count as evidence; AS9102 is the aerospace formalization. See the Qualification Plan Template.

Fretting — micro-motion wear that oxidizes contact surfaces under vibration, causing intermittent high resistance. See Common failure points and Low-Level Signal Contacts.

Front-release / rear-release — which side the contact insertion/extraction tool works from; rear-release (wire side) is the common 38999 arrangement. See Termination types.

Genuine vs. clone / "compatible" / "-style" — a clone or "-style" part resembles a named family without being the genuine article; it may mate perfectly, loosely, or not at all, with no drawing to arbitrate. Fine when chosen knowingly for a prototype; a trap when assumed. See JST Is Not One Connector and Marketplace Kits.

Ground-first sequencing — staggered contacts so ground mates first and breaks last, preventing power-before-ground faults. See Mating sequence and blind mate.

HCP / RADSOK — high-current power contact technologies (RADSOK = Amphenol's hyperboloid contact) for loads standard contacts can't carry. See Quick-Reference A3.

Hermetic — a gas-tight connector (often glass-sealed, solder-terminated) for pressure boundaries; distinct from merely IP-rated. See Solder-cup quality.

Housing — the insulating body that holds the contacts. In most families it is ordered separately from the contacts, and its gender is independent of theirs. See Buying the Right Mating Parts.

ICD — interface control document; the released definition of an interface (part numbers, pinout, limits, assembly) that procurement and manufacturing build from. See Configuration-control item.

IDC — insulation-displacement contact; a blade cuts through insulation to terminate, common for ribbon cable. See Termination types.

Insert arrangement — the defined layout of contact count, sizes, and positions inside a shell; the drawing that actually controls what a connector carries. See Insert arrangements.

Insulation diameter — the wire jacket's outside diameter. Crimp insulation wings and wire seals are sized for a range of it, independent of conductor gauge — the second number to check before crimping. See Crimping.

Insulation resistance — leakage resistance through the insulator (MΩ/GΩ); the first parameter to drop after moisture ingress. See Reading Datasheets.

IO-Link — a point-to-point digital sensor/actuator protocol carried over standard unshielded 3–4-wire sensor cabling. See M12 coding table.

IP rating — ingress-protection code (IEC 60529); applies to the tested, correctly-mated assembly, not automatically the system. See Quick-Reference A1.

IP69K — the high-pressure/high-temperature washdown rating from ISO 20653 (not IEC 60529, which has the IPx9 equivalent). See Quick-Reference A1.

Jam nut / flange mount — the two panel-mount styles: single rear nut (compact, can rotate) vs. perimeter bolts (rigid, better gasket control). See Jam nut vs. flange.

Keying / polarization — mechanical features that prevent mis-mating; alternate key positions stop identical connectors from cross-mating. See Service classes and keying.

Latch — friction vs. positive — friction fits hold by grip alone (Dupont, servo leads) and can walk off under vibration; a positive latch clicks in and must be deliberately released. Which one a connector has is both an identification clue and a reliability decision. See Identify an Unknown Connector.

Less-contact — a connector part number shipped without contacts; contacts and tooling must be ordered separately. See What a full 38999 interface includes.

Male / female — ambiguous by itself: the housing and the contacts each have a gender, and they often don't match intuition (a "female" housing can hold pin contacts, and vice versa). Say which you mean — or use pin/socket for contacts and plug/receptacle for bodies. See the pin/socket entry below and Connector Anatomy.

Mating cycles — the rated number of connect/disconnect cycles; design with margin below it, and remember it is not a ruggedness measure. See Quick-Reference A4.

Mating pair — the two halves designed to mate, defined by the family drawing. Buy both halves deliberately; never discover the mate by trial. See Buying the Right Mating Parts.

Mezzanine (board-to-board) — a connector pair joining two parallel PCBs at a defined mated stack height; ordered as a matched header/receptacle pair from one family's height table. See Board-to-board.

NRND — not recommended for new designs; the lifecycle state between active and end-of-life. Existing designs are supported, but the clock is running. See Lifecycle & Procurement.

Obsolescence / DMSMS — the loss or impending loss of a part's manufacturing sources (DoD language: diminishing manufacturing sources and material shortages); managed proactively with multi-source families and recorded alternates, or reactively at much higher cost. See Lifecycle & Procurement.

Open-barrel crimp — the common stamped-terminal crimp style with two wing sets: conductor wings folded onto bare strands (the electrical joint) and insulation wings gripping the jacket (the strain relief). Both must be formed correctly. See Crimping.

Panel mount — a connector mounted through an enclosure wall (jam nut, flange, or snap-in), making the enclosure part of the interface — panel sealing and cutout included. See Connector Anatomy.

PCN — product/process change notification; the manufacturer's notice that a part is changing (material, plating, site, marking) while keeping its part number. Harmless to most users — except when it touches your qualified configuration. See Lifecycle & Procurement.

Pigtail — a shield gathered into a short wire instead of a 360° bond; inductive, so it radiates at RF. See EMI, shielding, and bonding.

Pin / socket vs. plug / receptacle — contact gender (electrical) vs. body style (mechanical); all four combinations exist, so verify both on the part number. See Connector Anatomy.

Pitch — the center-to-center spacing between adjacent contacts; the most discriminating easy measurement on any connector. Measure across the whole row and divide by N−1. See Pitch: The Number That Saves You.

Plug / receptacle — body styles (roughly: the free/cable half vs. the fixed half), but vendors do not use the words consistently — verify against the drawing's mating diagram, not the terminology. Independent of contact gender. See Connector Anatomy.

Position / circuit / pin count — three names for the number of contact cavities in a housing, loaded or not. Count all of them when identifying a connector. See the identification workflow.

Pre-crimped lead — a factory-terminated wire you insert into a housing yourself; often the most reliable hobby choice for tiny contacts (SH/GH/PH class). See Crimping.

QPL — Qualified Products List; the register of parts qualified to a military specification. Required when qualification matters, and a second-source consideration always. See Production reality.

Qualification testing — design-level proving of one documented connector configuration (parts, plating, wire, seals, tooling, process), done once per the governing spec's rules — distinct from acceptance testing, which verifies every built unit or lot. See the Qualification Plan Template and the Harness Inspection Checklist.

Requalification — re-opening qualification evidence when the qualified configuration changes: a PCN touching form/fit/function, an alternate or vendor change, a new site or plating. The governing spec decides the scope; the question is never optional. See the Qualification Plan Template and Lifecycle & Procurement.

RMF — Molex's Reduced Mating Force Micro-Fit terminals; a mating-force feature, with current still set by the exact terminal P/N. See Micro-Fit deep dive, Comparison Matrix.

Scoop-proof — shell geometry where the outer shell engages before the pins, so a misaligned plug can't scoop across and bend them. See 38999 series distinctions.

Sealing plug — the plug that fills an unused contact cavity in a sealed connector; an unplugged cavity is an open hole. See Wire seals.

Service class — the 38999 designator controlling shell material, plating, and environmental capability. See Service classes and keying.

Shield / drain wire — the cable's braid/foil EMI barrier, and the bare conductor that terminates a foil shield. Termination strategy (one end / both ends / 360°) is system- and frequency-dependent — see EMI, shielding, and bonding §5.7.

Shrouded header — a pin header surrounded by a plastic wall, adding polarization, latch engagement, and pin protection that bare 0.1 in headers lack. See Internal PCB harnessing.

Slash sheet — the numbered detail sheet under a military specification (e.g. D38999/26…) that defines a specific connector style. See Decoding a part number.

Solder cup — a solder-terminated contact with a cup behind it; reworkable but skill-sensitive and strain-relief-dependent. See Solder-cup quality.

Stack height (mated height) — the board-to-board distance a mated connector pair sets between two PCBs; the defining board-to-board spec, offered in multiple heights under near-identical part numbers — order the matched pair to it. See Board-to-board.

Strain relief — the hardware that transfers cable load into the connector body so the contacts never carry it. See Connector Anatomy.

Temperature rise — the heating above ambient a contact system is allowed at its rated current; the hidden variable behind every current rating and derating curve. See How to read a derating curve.

TPA — Terminal Position Assurance; a secondary lock confirming every contact is fully seated before the connector can mate. See Major Connector Categories.

Traceability / CoC — the documented chain from factory to your dock (certificates of conformance, lot records) that authorized distribution provides by default and broker purchases must prove per lot. See Lifecycle & Procurement.

Voltage rating — a class figure tied to insulation, spacing, and test conditions; working voltage and withstand voltage (DWV) differ, and AC/DC/altitude assumptions matter. Verify the datasheet. See Reading Datasheets.

Wedgelock — the separate wedge (orange on gray DEUTSCH DT plugs, green on receptacles) that locks contacts into their cavities as the secondary retention; a DT-family connector without it has no retention system. Usually a separate line item. See DEUTSCH Deep Dive.

Wetting current — the relay/switch-world concept of the minimum load a film-forming contact needs to stay reliable; below it, tin-class contacts drift intermittent. Gold-class contacts effectively have none in clean service — the reason they own dry-circuit duty. See Low-Level Signal Contacts.

Wire gauge (AWG / mm²) — conductor size. Every contact supports a defined gauge range, and both the electrical load and the crimp quality depend on staying inside it. See Crimping.

Wire seal / grommet — the per-contact seal sized for a specific wire-OD range; undersized wire defeats the whole connector's sealing. See Wire seals.