* 言葉 (kotoba): This is the most common and general translation, referring to a word, a phrase, or language in general. It's the best choice in most situations.
* 単語 (tango): This refers specifically to a single word, like a vocabulary item. Use this when you're talking about individual words in a dictionary, for example.
* 語 (go): This is a more formal and literary word for "word," often used in compound words.
Therefore, without knowing the context of how you're using the word "word," 言葉 (kotoba) is likely the best translation.