In French, the word for hair is cheveu (singular) and cheveux (plural).
The term cheveu refers specifically to a single strand of hair, while cheveux is used when talking about hair in general or multiple strands. For example, you might say J’ai de beaux cheveux, which means ‘I have beautiful hair.’
Remember, nouns in French also have a gender, and cheveu is masculine, so we say le cheveu for ‘the hair.’