He do is incorrect, because to do

Morphological typology
There are roughly four kinds of morphologies that languages use: Analytic, Inflectional, Agglutinative, and Polysynthetic. Morphological classifications are made based on how the morphology of the language works, that is, how are words formed, combined, and inflected (if they are).
Analytic languages are not inflected, that is, nouns and adjectives are not declined and verbs are not conjugated. Instead, the order of the words determines grammatical relationships. English is an analytical language, though not perfectly so, because there are some agreement markers, tenses, etc. in English. For example, *he do is incorrect, because to do must be inflected to mark third person singular subject: he does. Chinese can also be said to be an analytic language, though words are so little inflected in Chinese, that some would classify it as a minimal grammar language. This is incorrect, since what languages lack in inflection (or morphology) they must make up in word order, or syntax; in a technical sense, both morphology and syntax are considered to form parts of grammar. Both English and Chinese rely on syntax, word order, to show grammatical relationships, e.g. the subject must be in a certain position relative to the verb (in English, it must precede it).
Inflectional languages are different from analytic languages, because they do inflect (as the name suggests) quite a lot. A good example is Latin, in which most words are marked up and down for all kinds of tenses, moods, cases, agreements, and more. When the words in the sentence are inflected to show agreement with all their subjects, objects, and other arguments, then word order becomes very fluid. Whereas analytical languages rely on strict word order, inflectional languages have flexible word order.
Agglutinative languages are those in which words can be combined easily. For example, instead of saying the shoe of the horse, agglutinative languages say horseshoe. Agglutinative languages include German and Turkish. In these languages, new words are formed by combining old ones, so that words can become very long, but also contain a lot of information. This kind of morphology is called productive, because new words are formed in a predictable manner. Agglutinative languages can have both lots of agreements and inflections, or have rigid word order, such as German.
The last kind of morphological category, polysynthetic languages, is the least understood by linguists, because none of the major written languages in the world today, such as English, Chinese, Russian, Arabic, Hindi, etc., are polysynthetic. Some Native American languages in North America, such as Navajo, and some Polynesian languages are polysynthetic. Words, especially verbs, in these languages also tend to become very long, because every argument in a sentence is inflected on the verb, but also on other words with an argument structure, such as prepositions. These languages are very difficult to learn, not only because they are not properly understood, but also because one verb has literally hundreds of inflections. For example, the average Navajo verb has about 15 categories of prefixes, and a couple of affixes. These categories in turn, have between six and 200 members. In addition, the affixes can move around and change in agreement with other prefixes.