Short answer: Article 90 tells you what the NEC covers, what it leaves out and how to read it: “shall” is a requirement, “shall be permitted” is an option, and informational notes are not rules. Article 100 holds the definitions. Apprentices most often mix up listed and labeled, grounded and grounding, branch circuit and feeder, and continuous load.
Definition questions look easy until two terms sound alike. The PSI outline puts Code Definitions in the first subject area of the Texas Journeyman NEC Knowledge part. The Texas Journeyman Practice Pack has 1,000 practice questions on the 2026 NEC, and 10 timed two-part mocks. Use it with your own code book to practice finding each term and rule. US$39 once.
Tsai Electro is an independent learning site. Not affiliated with TDLR, PSI or NFPA. We explain the code in our own words and do not reproduce NEC text. Always read the rule in your own 2026 NEC.
Which NEC edition applies in Texas
Texas adopted the 2026 NEC as the state electrical code, effective September 1, 2026, with a limited exception for GFCI protection of certain outdoor outlets (TDLR rule adoption notice). The PSI bulletin for TDLR says the electrician exams are referenced to the 2026 NEC from the same date, and the exam is open book with your own soft-bound copy (PSI Candidate Information Bulletin, TDLR exam page).
That matters for definitions. If you study from a 2020 or 2023 book, some terms sit in different places and a few have new wording. The City of Denison’s summary of 2026 changes, for example, notes revised definitions that separate the different kinds of bonding jumpers, and a new Article 120 that now holds the load calculations that used to be in Article 220 (Denison 2026 NEC summary).
Article 90 in plain words
Article 90 is the introduction to the code. It is short, and most apprentices skip it. Read it once, because it explains how every other article works.
| Topic | What it means for you | Where to look |
|---|---|---|
| Purpose | The NEC is about practical safety from electrical hazards. It is not a design manual and not a course for untrained people. | 90.1 |
| What is covered | Wiring and equipment in buildings, structures, yards, lots and similar premises, plus the conductors that connect them to the supply. | 90.2 |
| What is not covered | Examples: ships, aircraft, rail rolling stock, underground mines, and utility-owned installations under the utility’s exclusive control. | 90.2 |
| How the chapters fit | Chapters 1 to 4 apply everywhere. Chapters 5, 6 and 7 add to or change those rules for special occupancies, equipment and conditions. Chapter 8 (communications) stands on its own unless it points back. Chapter 9 holds tables. | 90.3 |
| Who decides | The authority having jurisdiction (AHJ), usually the inspector, interprets the code and approves equipment and installations. | 90.4 |
| Rule language | “Shall” or “shall not” is required. “Shall be permitted” is allowed but not required. Informational notes explain; they are not enforceable. | 90.5 |
The arrangement row is the one that saves you on the job. If a rule in Chapter 6 (for example, swimming pools) says something different from a general rule in Chapter 2, the Chapter 6 rule wins for that installation.
10 definitions apprentices mix up
Since the 2023 edition, almost every definition in the NEC sits in one alphabetical list in Article 100, instead of at the start of each article. If you cannot find a term, look in Article 100 first, then use the index. The meanings below are our own short explanations, not the code wording.
| Term | What it means in plain words | Common mix-up |
|---|---|---|
| Approved | Acceptable to the AHJ. | Thinking “listed” and “approved” are the same thing. The inspector approves; a testing lab lists. |
| Listed | The product is on a list published by an organization the AHJ accepts, which tests products and checks production. | Confusing it with “labeled”. |
| Labeled | The product carries that organization’s label or mark. | A listed product is usually labeled too, but the two words mean different things. |
| Readily accessible | You can reach it quickly without climbing over things, removing obstacles or bringing a portable ladder. | Plain “accessible” is a weaker condition. |
| Branch circuit | The conductors from the final overcurrent device to the outlets. | Calling a panel-to-panel run a branch circuit. That is a feeder. |
| Feeder | Conductors between the service equipment (or a separately derived system or other source) and the final branch-circuit overcurrent device. | Missing that a subpanel is fed by a feeder. |
| Grounded conductor | A circuit conductor that is intentionally connected to ground, usually the white neutral. | Mixing it up with the equipment grounding conductor. |
| Equipment grounding conductor | The green or bare conductor that ties metal parts to the grounding system and carries ground-fault current so the breaker can trip. It does not carry normal load current. | Calling it “the ground” and treating it like the neutral. |
| Continuous load | A load where the maximum current is expected to last 3 hours or more. | Treating every large load as continuous, or forgetting the 3-hour test. |
| Qualified person | Someone with the skills and knowledge for the equipment and safety training to recognize and avoid the hazards. | Thinking a license alone makes you qualified for a specific task. |
Two more to watch: a neutral conductor is always a grounded conductor, but not every grounded conductor is a neutral. And “ampacity” is the current a conductor can carry continuously under its conditions of use without going over its temperature rating, so the same wire can have different ampacities in different places.
Worked example: does the continuous-load rule apply?
Many sizing rules add 25% for continuous loads. For branch circuits, the overcurrent device must be at least the noncontinuous load plus 125% of the continuous load (210.20(A)). The definition decides whether that extra 25% applies.
- A commercial sign circuit draws 16 A and runs 12 hours every night. 12 hours is 3 hours or more, so it is a continuous load.
- Minimum overcurrent device: 16 × 1.25 = 20 A. 20 A is a standard size.
- A shop air compressor draws 16 A but runs about 20 minutes at a time. That is less than 3 hours, so it is not continuous by this test.
- Minimum overcurrent device from this rule alone: 16 A. Motor rules in Article 430 still apply to the compressor motor.
Check: 20 ÷ 1.25 = 16. Same load, so step 2 is right.
How to look up a definition fast
- Turn to Article 100. Terms are in alphabetical order.
- If the term is not there, check the index at the back of the book under the main word (for example, “Conductors, grounded”).
- Read the full definition, then read the rule that sent you there again. Most definition questions are really about one word in a rule.
- On the exam, you cannot write in your book during the session, but PSI allows notes and highlighting made before the exam and publisher-made tabs (PSI bulletin). Mark Article 100 before test day.
Check yourself
Our own practice questions. Answers below each.
- A parking-lot lighting load of 12 A runs from dusk to dawn. Continuous or not? Answer: Continuous (3 hours or more). Minimum overcurrent device from the branch-circuit rule: 12 × 1.25 = 15 A.
- A product has a mark from a testing lab on it. Which word describes that mark? Answer: Labeled.
- You run conductors from the main panel to a garage subpanel. Branch circuit or feeder? Answer: Feeder. Branch circuits start at the final overcurrent device in the subpanel.
- Is an informational note in the NEC a requirement? Answer: No. It explains or points to other material.
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The code book for definitions
NFPA 70, National Electrical Code (NEC), 2026 Edition, softbound. Articles 90 and 100 are in it. Read each definition in your own copy before you rely on it.
FAQ
What is NEC Article 90?
Article 90 is the introduction to the National Electrical Code. It explains the purpose of the code, what installations it covers and does not cover, how the chapters relate, who enforces it, and how to read mandatory rules, permissive rules and informational notes.
Where are definitions in the 2026 NEC?
Almost all definitions are in Article 100, in alphabetical order. This has been the arrangement since the 2023 edition. If a term is not there, use the index at the back of the code book.
What is the difference between listed and labeled?
Listed means the product appears on a list published by a testing organization acceptable to the inspector. Labeled means the product carries that organization’s label or mark. They are related but are separate terms.
What counts as a continuous load in the NEC?
A load where the maximum current is expected to continue for 3 hours or more. Many sizing rules then require the overcurrent device or conductor to be sized at 125% of that load.
Sources checked October 2026
- TDLR rule adoption notice, 2026 NEC: https://www.tdlr.texas.gov/news/rulemaking/2026/09/01/commission-adopts-rules-12/
- TDLR exam page: https://www.tdlr.texas.gov/electricians/elecexam.htm
- PSI Candidate Information Bulletin for TDLR (updated 9/15/2026): https://test-takers.psiexams.com/api/content/bulletin/1682
- City of Denison, 2026 NEC significant changes: https://denisontx.gov/DocumentCenter/View/4131/2026-National-Electrical-Code-Significant-Changes
- NFPA 70 (NEC), 2026 edition, Article 90 and Article 100, read in your own copy: https://www.nfpa.org/codes-and-standards/nfpa-70-standard-development/70
