Sorry for a rather belated reply, Kiranga! I wasn't alerted that you had replied to my earlier posting; so it wasn't until recently, when returning to the thread, that I bumped into this posting of yours.
The grammar terms ''infinitive present tense verb'' and ''adjective verb'' are nonexisting, to begin with. There's a whole world of difference between infinitives and verbs not only in application but also in appearance, and the same holds true for adjectives and verbs. I'm even impatient to learn the name of grammar book or source from which you obtained them so I perhaps might bring the matter to the attention of the author to prevent other readers from further being misled.
Further, your assertion that the word ''struggle'' is primarily a verb is decidedly iffy and frivolous. There simply is no such thing as ''the primary definition of a word.'' In English language, words are assigned to a particular part of speech only by looking at how they behave in a given sentence rather that at how they are traditionally used. That's why ''in,'' for instance, which is conventionally a preposition, is rightly acting as an adjective modifying noun ''brand'' in the sentence ''This brand of car is no longer in nowadays.'' I've no doubt that you meet lots of words so behaving in your daily reading or listening.
I'm shocked, truthfully speaking, that you're having a difficult time telling whether or not ''struggle'' is a noun in ''Development is struggle.'' For any person with a very basic grammar understanding, breaking up that sentence into its ingredients in the following manner should really be a pushover:
Development= subject
Is= linking verb
Struggle= subject complement
In addition to all ''be'' verbs, linking verbs include ''feel,'' ''smell,'' ''sound,'' ''look,'' ''seem,'' ''taste,'' and ''become.'' Others are ''go,'' ''remain,'' ''stay,'' ''turn,'' ''lie,'' ''appear,'' ''get,'' ''prove'' and ''run.'' Their main office is, in the same way as ''be'' does in the sentence under discussion, to connect the subject to a complement, which is a word or group of words that completes a predicate. Subject complements always take the form of ''noun,'' ''pronoun,'' or ''adjective''; and the rule of thumb is that whenever there's a linking verb, there's surely one of those three.
As to to what it is that makes ''Terrorism is theatre'' grammatically acceptable while regarding ''Education is struggle'' as a flawed construction, I don't think the rules have changed. My assumption, though, is maybe that sentence has been used as a book title or anything similar to that. If that is the case, there's nothing wrong about it. In the journalism or literature works, it's allowable for articles as well as ''be'' verbs to be eliminated from titles entirely for the sake brevity. You might have already seen plenty of news headlines written in that way in English newspapers or magazines.
Radhia Sweety,
The vagaries of different obligations and schedules, coupled with the rapid fire pace of posts at JF, provides a jointly sufficient and genuine excuse for you to not see my reply at all. I am delighted that you have, for your input is rather interesting to some of us with a barely passable knowledge of this strange tongue. Let me point out from the onset that your input is much appreciated. It attempts to answer my yearning for a grammatically rooted approach, complete with pointers to the specific rules regarding the different parts of speech and the correct/ acceptable usage.
Indo-European languages, having evolved traceably from Indo-Aryan languages / Sankrist, carry with them a logic and grammar structure alien to Bantu language speaking (as a mother tongue) people. English particularly, being a lingua-franca of world import in addition, is a kaleidoscopic smorgasbord of a language, it is - to my meagre knowledge in matters linguistic- particularly taxing. I am sure there is some high German that could prove even more taxing to someone with the opportunity and inclination to investigate. In this I carry the disadvantage of being neither a professional linguist nor a related language teacher at any level.
Before your input, I took great care - perhaps at the risk of disappointing some of my overenthusiastic admirers- to point out that I am but a lowly student in this cumbersome tongue, and in repeating one of my common mantras that is about to take a Vedic frequency in my writings here, I reasserted that the only reason anyone would bestow disproportionate and frankly speaking embarrassingly unwarranted amounts of praise on my part would be due to a low common standard to begin with.
By "infinitive present tense verb" I meant a present tense infinitive verb, which would have matched "To develop is to struggle".
An adjective verb is a very real thing in English as postulated at
Verbs Can Become Adjectives, perhaps you would care to critique. I can see the presentation as "adjective verb" posing a wanting duality. The fluidity exposed below -indeed pointed by you in your post- will further attest.
As for the word "struggle" being primarily a verb, I am going by the previously given
Dictionary.com - Free Online English Dictionary . I still do not have the link to your online handbook.
The notion of a verb / adjective (perhaps butchered in being presented as "adjective verb") will do well to illustrate the fluidity of what part of speech a word is, per specific use, as deciphered in your input. If I can appreciate the wave particle duality of photons, I can surely appreciate this. In my case "primarily" merely denotes the dominant usage per the authority of a given source, in this case as given by
Dictionary.com - Free Online English Dictionary, not necessarily the most correct usage.
I saw the pushover you are referring to, it troubled me to no end. I even ran the sentence at
grammarly, and the only flag they had was a wrong verb form use. This is what led me to question the automated notion that "struggle" was used as a noun, because it is possible the word is being used as another part of speech. To draw from a horrid American example (for purists at least), it is not entirely strange to hear someone quite educated, and a mother tongue English speaker saying something like "We summer in Long Island" ( "summer" as a verb, the evolution of the English language!). I was eliciting further input on the possibility of "struggle" being used differently from the traditional and expected noun. I was tempted to say adjective but the stark juxtaposition with "struggling" would have proved too much.
However right you may end up being, you still have not explained why "Terrorism is theatre" is grammatically acceptable while "Education is struggle" is not. Drawing from your original objection, theatre is a countable noun, so we should have either "Terrorism is a theatre" or "Terrorism is theatres" but not "Terrorism is theatre". This is if you want to go with the purist construction.
The sentence, as given to the JF public, appeared on some banner/ billboard, so there is a whole lot of poetic license towards economy of words and a more succinct expression as alluded in the last part of your input. Is this equally responsible for "Terrorism is theatre" ? Is that your meaning when you wrote "I don't think the rules have changed"?
If I have quoted Shaw ridiculing the English language numerous times before for its idiosyncratic logic - even to an Irishman- and a more than generous amount of avenues for exceptions in its lexicon, nomenclature and grammar, it is not without cause.
All in all, let's raise the bar of discussion and hopefully learn.
