Here's what you might be referring to:
1. Verbs that don't change form for tense:
* Modal verbs: These verbs, like *can*, *may*, *should*, etc., express possibility, permission, obligation, etc., and do not change their form to show tense. For example, *I can go* and *He can go* both use the same verb form.
* Auxiliary verbs: These verbs help other verbs to form tenses and moods, but they don't express tense themselves. Examples include *be*, *have*, and *do*.
* Some irregular verbs: Some irregular verbs, like *cut*, *put*, *let*, and *set*, have the same form for both present and past tense.
* Some languages: In some languages, verbs might not explicitly change form for tense, relying on context or other elements to indicate the time of the action.
2. Verbs that express a state, not an action:
* Stative verbs: These verbs describe a state of being, feeling, or possessing, rather than an action. They are often not used in progressive tenses. Examples include *know*, *love*, *own*, *believe*, and *seem*.
3. Verbs that are considered "tenseless" in some theories of grammar:
* Some linguists: There are linguistic theories that argue that tense is not a fundamental grammatical category, but rather a complex interplay of different elements. In these theories, some verbs may be considered "tenseless" in the sense that they do not express a specific point in time but rather a more general state or situation.
It's important to note that:
* The term "non-tense verb" is not widely used in traditional grammar.
* The concepts of modal verbs, auxiliary verbs, and stative verbs are well-established and relevant to understanding the way verbs function in sentences.
If you can provide more context about what you are interested in, I can give you a more specific answer.