Velu vs. poilu
The French words poilu and velu both translate to hairy, but they are not fully interchangeable. The main difference lies in the nature of the hair they describe and their connotations. Velu is a general, neutral term for a surface covered in fine hair, while poilu often implies coarser, more prominent hair and has a significant historical meaning.
Velu
A2Velu is the most general term for hairy. It describes a surface covered with hair, which is often soft, fine, or downy. It is a neutral word that can be used for people, animals, and even plants.
Il a le torse velu, comme beaucoup d'hommes de sa famille.
(He has a hairy chest, like many men in his family.)
La peau de la pêche est douce et velue.
(The skin of the peach is soft and fuzzy.)
Une étrange chenille velue traversait le sentier.
(A strange hairy caterpillar was crossing the path.)
Le tissu de ce fauteuil a un aspect velu très confortable.
(The fabric of this armchair has a very comfortable velvety feel.)
Poilu
B1Poilu also means hairy, but it typically refers to hair that is thicker, longer, or coarser. It is used almost exclusively for people and animals, not plants. It can imply a certain ruggedness or virility, and depending on the context, can be slightly informal. Crucially, un Poilu (with a capital P) is the famous nickname for French infantry soldiers in World War I.
Mon grand-père était un Poilu et a combattu à Verdun.
(My grandfather was a French WWI soldier and fought at Verdun.)
Après un mois sans se raser, ses jambes étaient très poilues.
(After a month without shaving, her legs were very hairy.)
Ce n'est pas un chaton, c'est un gros matou bien poilu.
(That's not a kitten, it's a big, very hairy tomcat.)
Il se plaint d'avoir le dos trop poilu.
(He complains about having a very hairy back.)
Summary
In summary, use velu for a general description of a surface covered in hair, especially if it's fine or soft, and it's the only choice for plants or fabrics. Use poilu to describe more prominent, thick, or coarse hair on people and animals. While a man's chest can be described as both velu and poilu, a peach can only be velue. Remember the specific historical meaning of Poilu as a French WWI soldier.