How do you say feces in French?

The most common and direct translation of "feces" in French is "excréments".

However, it's important to note that "excréments" is a rather formal word. In everyday conversation, you might use other words like:

* "caca" (informal, especially for children)

* "merde" (vulgar)

* "selles" (more clinical)

The best choice will depend on the context and your desired level of formality.