In modern English, we chiefly encounter a in a role of an indefinite article. In Spanish, a is one of the most common words that serves as a preposition. In Russian and some other Slavic languages, а (or a; Cyrillic letter а looks exactly like Latin a) is an interesting conjunction which may variably mean “and”, “and yet”, “but”, “whereas” or “while”.
In physics, a is a common symbol for acceleration. For example, Newton’s second law can be written as
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