Japanese is not as clear-cut as the previous answer suggests. Although "ai" is the most general term meaning "love", it depends very much on the context etc., which term you would use. The meaning of "ai" can range anywhere from "charity" to "passion", For example, "aichaku" means "love" in the sense of "attachment", "affection", whereas "ren'ai" means "love" in the sense of "tender passion" or "amour if you want.
Thus, you might want to specify your question.

Noun: 愛(ai)、愛情(aijoh)、愛着(aichaku)、好意(kou-I)、恋(koi)、色情(shikijou)、恋人(koi-bito)、愛人(ai-jinn), （よろしくとの）挨拶 (yoroshiku – greeting), 性欲(sei-yoku)、情事(jou-ji)、性交(sei-kou), ゼロ(zero)

Verb: 〜を愛する (ai-suru)、かわいがる (kawai-garu)、大事にする(daiji-ni-suru)、恋する (koi-suru)

Origin=l'oeuf (egg in French)