Reference

Captain's license glossary

The acronyms every course seller uses without expanding them, defined plainly and in the order they matter to a first-time applicant.

Assessment period: A recommended waiting time after a criminal conviction, published in tables at 46 CFR 10.211, that the National Maritime Center applies before normally granting a credential. It runs from completion of the sentence and is longer for more recent or more serious offenses. Eligibility with a record.
Code of Federal Regulations (CFR): The published U.S. federal regulations. Merchant mariner credentialing, including sea-time credit and the OUPV and Master requirements, is governed largely by Title 46 of the CFR, Part 11.
Gross Register Tonnage (GRT): A measure of a vessel's internal volume, not its weight, used to set the Master license tiers (25, 50, and 100 Ton). The tonnage of the vessels you served on and the vessel you intend to operate affects which Master tier you qualify for.
Inland route: A route designation for inland waters, bays, sounds, and Great Lakes service. You earn an Inland endorsement from sea time documented on those waters. It does not extend offshore, so it is narrower than a Near Coastal endorsement. How sea time sets your route.
Master license: A captain's license that authorizes commanding an inspected vessel and carrying more than six paying passengers, tiered by vessel tonnage as Master 25, 50, or 100 gross register tons. The tier you earn depends on documented sea time on vessels of qualifying size. OUPV vs Master.
Merchant Mariner Credential (MMC): The single federal document issued by the U.S. Coast Guard National Maritime Center that authorizes a person to work aboard a U.S. vessel. The captain's license is an officer endorsement, such as OUPV or Master, printed in this credential.
National Maritime Center (NMC): The U.S. Coast Guard unit that evaluates applications and issues the Merchant Mariner Credential. The NMC makes the final determination on eligibility, sea-time credit, and medical fitness for every captain's license.
Near Coastal: A route designation covering ocean waters generally out to 100 nautical miles offshore. You earn a Near Coastal endorsement when enough of your documented sea time was on near-coastal or ocean waters, and it also lets you work inland waters. OUPV routes explained.
Operator of Uninspected Passenger Vessels (OUPV): The entry-level captain's license, commonly called the six-pack because it allows carrying up to six paying passengers on an uninspected vessel. It is issued as either an Inland or a Near Coastal route depending on where your sea time was earned.
Regional Examination Center (REC): A local U.S. Coast Guard office where mariners submit applications, verify identity, and take exams. Your application routes through an REC before evaluation at the National Maritime Center.
Small Vessel Sea Service Form (CG-719S): The Coast Guard form that documents your sea time, filled out per vessel and signed by that vessel's owner or operator (or self-certified if you own it). It records the days, water type, and tonnage the National Maritime Center evaluates. The CG-719 forms walkthrough.
Standards of Training, Certification and Watchkeeping (STCW): An international convention setting minimum training and certification standards for mariners. Some captain's license routes and larger tonnage or offshore endorsements require associated STCW certificates such as basic training.
Transportation Worker Identification Credential (TWIC): A biometric security card issued by the Transportation Security Administration that most merchant mariners must hold. You generally need a TWIC before or alongside your captain's license application, and it has its own separate processing time.