A homophone is a word that is pronounced the same (to a varying extent) as another word but differs in meaning. A homophone may also differ in spelling. For example, the two words may be spelled the same: rose (flower) and rose (past tense of rise), or differently, as in rain, reign, and rein.

English Grammar Terms II

In linguistics, the grammar of a natural language is its set of structural constraints on speakers 'or writers' composition of clauses, phrases, and words. The term can also refer to the study of such constraints, a field that includes domains such as phonology, morphology, and syntax, often complemented by phonetics, semantics, and pragmatics. There are currently two different approaches to the study of grammar, traditional grammar and theoretical grammar.