Verb is a word that is not easy to define. Here are some of the attempts that have been made over the last 2,400 years.
( c428-347 BCE) Plato: A sign expressive of an action is what we call a verb.
( d.322 BCE) Aristotle: A verb is a […] composite significant sound, marking time. For “man” or “white” does not express the idea of “when”; but “walks” or “has walked “ does connote time, present or past.
( b. c166 BCE) Dionysius Thrax: The verb is the part of speech without case inflection, admitting inflections of tense, person and number, signifying an activity or a being acted on.
(6th century ACE) Priscian: The verb is a part of speech with tenses and moods, but without case [the noun is inflected for case], that signifies acting or being acted upon ... .
17th to 19th Centuries ACE
(1660) Arnauld A. and Lancelot C.: [A verb] is a word whose main use is to signify affirmation, that is to say, to point out that the discourse in which this word is used is the discourse of a man who does not only conceive things, but also judges and affirms them, [.... a verb also expresses ...] other movements of the soul, like wishes, requests, command, etc,
(1711) Gildon, Charles and Brightland, John: ... the very Essence of [a verb] is express'd in the term Affirmation, since all Words of this kind do affirm Something of Something..... An Affirmation (as the Word does show) / Something affirms, and does Number know, / And Time and Person; whether it express / Action, Being, Passion; or their Want confess.
(1755) Johnson, Samuel: A part of speech signifying existence, or some modification thereof, as action, passion. And withal some disposition or intention of the mind relating thereto, as of affirming, denying, interrogating, commanding.
(1761) Priestley, Joseph: A VERB is a word that expresseth what is affirmed of, or attributed to, a thing; as I love, the horde neighs,
(1762): Lowth, Robert: A VERB is a word which signifies to be, to do, or to suffer.
(1785) Ash, John: A Verb is a word that signifies the Acting or Being of a Person, Place or Thing; as, the Man calls, the City stands, the Tree falls, I am
(1794) Murray, Lindlay: A VERB is a word which signifies to BE, to DO or to SUFFER; as, "I am, I rule, I am ruled."... .
(1823) Cobbett, William: Verbs are, then, a sort of words, the use of which is to express the actions, the movements, and the state or manner of being, of all creatures and things, whether animate or inanimate.
(1828) Webster, Noah: VERB, In grammar, a part of speech that expresses action, motion, being, suffering, or a request or command to do or forbear any thing. The verb affirms, declares, asks or commands; as, I write; he runs; the river flows; they sleep; we see; they are deceived; depart; go; come; write; does he improve?
(1870) Angus, Joseph: A verb is a word that says or affirms something: 'being, doing, suffering; 'being, act, state.'
(1882) Mason, C. P.: A verb is a word by means of which we can say something about some person or thing.
(1890) Morris, Dr R.: A Verb is a word that states or affirms what a thing does or is done to, or in what state it exists; as, "the fire burns," John is beaten," "the child sleeps," "the fun begins."
(1891-8) Sweet, Henry: The primary use of verbs as regards their meaning is to express phenomena (changing attributes), as in come, all, grow, die [compare the permanent attribute-word dead]walk strike, see live, think. In other verbs the idea of phenomenality is less predominant, as in live, shine – compared with flash, twinkle; stand – compared with fall, rise; lie, sleep. In exist, which is the most abstract and general of al verbs that have an independent meaning, we can realise the sense of phenomenality only by the contrast with non-existence.
(1904) Daniel, Rev. Canon Evan: A verb (Lat: verbum, a word) is the part of speech by means of which we make affirmations. It was so called as being pre-eminent the word in a sentence. Verbs are used to express(1) what a thing does, as 'the tree grows;' (2) what is done to a thing, as 'the tree is felled;' (3) in conjunction with a noun or adjective, to express what a thing is becomes or seems to be. as ' he is a sailor; She became queen; They seemed happy.'
(1913) Webster's Revised Unabridged Dictionary: A word which affirms or predicates something of some person or thing; a part of speech expressing being, action, or the suffering of action. &hand; A verb is a word whereby the chief action of the mind [the assertion or the denial of a proposition] finds expression. Earle. Active verb, Auxiliary verb, Neuter verb,
(1954) Wood, Frederick T: A verb is a word which tells what someone or something does or is.
(1957) , Joshua: VERB Part of speech expressive of a state, being, process or action, e.g.. is, kills..
(1961) Webster’s Third New International Dictionary): a word belonging to that part of speech that characteristically is the grammatical center of a predicate and expresses an act, occurrence , or mode of being and that in various languages is inflected for agreement with the person and number of the subject, for tense, for voice, for mood, or for aspect and that typically has rather full descriptive meaning and characterizing quality but is in some instances nearly devoid of such meaning and quality esp. in use as an auxiliary or copula.
(1969) Christophersen, Paul & Sandved Arthur O.: Any word that can occur in the paradigm save - saves - saving - saved - saved sing - sings - singing - sang - sung will be called a verb. [...] the following group of words, which are traditionally included among verbs, can hardly said to be verbs in our analysis: can, could, may, might, must, ought, shall, should, will, would. They do not occur in the paradigm of save and sing. [...] None of the forms listed above is ever found with the other suffixes used to define verbs. It would perhaps be possible to regard them as a highly specialised type of verbs, but we shall not do that.
(1970) Schibsbye, Knud: VERBS In practice it is not difficult to distinguish this part of speech; it is generally agreed that it comprises such words as be, have, must, take, live, touch, spend But it is difficult to define the class. If we take he form as our basis we might, for instance, fix on the suffix –s in the 3rd pers. sing. present, but this would exclude can, may etc. Another form criterion that seems applicable is the difference in the expression of present and past: live/lived. fight/fought. But this definition would not cover put, set, etc. If we distinguish according to function, verbs could be defined as the sentence-forming element of a word-group. God in his heaven is not a sentence; God is in his heaven is. But this definition would not include infinitives, gerunds and participle. To be or not to be, that is the question / Erring is human / A sinking ship / Lost horizon. A wider definition on this basis could be obtained by regarding the nexus-forming element of a group as a verb. This formulation would cover some more of the verbal forms mentioned above: I found him missing / I expected him to be dead. But this definition is likewise unsatisfactory, since in a sentence such as don't speak with your mouth full the term nexus is applied to your mouth full. A definition by content is the most comprehensive, but also the vaguest. One might say that verbs express 'behaving' – partly in the sense of the subject manifesting itself (in the case of verbs used intransitively): he works / lived: partly of the way the subject behaves towards somebody or something else: he loves / loved her(in the case of verbs used intransitively). – In the first case the dividing line between verbs and adverbs will become blurred, as can be seen in he up and struck me; in the second case the dividing line between verbs and prepositions; compare A. versus B. and A. playing B. where versus and playing may be said to express the same relationship.
(1984) Chalker, Sylvia: Verbs are defined partly by position/function and partly by inflection. To oversimplify greatly, we can say that any word that fulfils the following two conditions is a verb: 1. Position Any single word that can fit into one or more of the following patterns and make a complete sentence (with no further words): (a) clever, [adj] the boy . . . (b) carefully. [adv] (c) the dog [noun phrase] eg (a) is, seems, looks; (b) works, wrote, spoke; (c) has, loved, hits, fed. 2. Inflection Any word that has a set of inflections similar to the following: walk walked walked walks walking begin began begun begins beginning [...] This two-fold definition partly fits BE/DO/HAVE. But it totally excludes a number of other words (eg can, must) because (a) they cannot be used alone except when a verb is ellipted [...] and (b) they do not have a set of inflections as in 2 above. Yet these words always form groups with verbs, and they share some of the formal characteristics of BE/DO/HAVE. (eg negative and question formation). So, it is reasonable to classify them as a sub-division of verbs.
(1989) Oxford English Dictionary (2nd Edition): That part of speech by which an affirmation is made, or which serve to connect a subject with a predicate.
(1992) Richard, Jack C. et al: verb /vз:b, vз:rb/n (In English) a word which (a) occurs as part of the PREDICATE of a sentence, (b) carries markets of grammatical categories such as TENSE, ASPECT, PERSON, NUMBER and MOOD, and (c) refers to an action or state. For example: He opened the door Jane loves Tom.