Both mean thin, but the tone differs sharply. Slim is a compliment — "she has a slim, athletic build" — while skinny is blunt and often suggests underweight: "he's gone skinny since the illness." If you are describing a person to their face, slim is the safe word.
The core difference
This pair is about attitude, not measurement. Two people of identical build can be called slim or skinny depending entirely on how the speaker feels about it. Slim implies the thinness is trim, deliberate and becoming. Skinny implies there is not quite enough of the person — bony, undernourished, a bit fragile.
Using slim
- He's kept a slim figure into his sixties.
- The jacket has a slim cut through the waist.
Slim also stretches to mean small in quantity, where thinness is only metaphorical: a slim chance, slim pickings, a slim majority, a slim volume of poetry. Skinny never does this job.
Using skinny
- She was a skinny kid who ate constantly and never gained a pound.
- Those skinny chair legs will never take the weight.
Applied to objects, skinny just means narrow and carries no sting — skinny jeans, a skinny tie, a skinny latte. The negative charge only appears when the subject is a person's body.
The test
Ask whether you could say it as praise. "You look slim" is a compliment in almost any company; "you look skinny" reads as concern or criticism, and often prompts the reply "is that a bad thing?" If you intend approval, choose slim. If you intend to flag that someone is too thin, skinny is the honest word — but say it kindly.
The edge cases
Skinny has been reclaimed in food and fashion marketing, where it signals low-calorie or narrow-cut rather than underweight: skinny syrup, skinny fit. That commercial use is neutral. It has not made the word neutral when applied to bodies.
There is also a fixed idiom worth knowing: the skinny means the inside information — "give me the skinny on the new manager." It is chiefly American and has nothing to do with body shape.
Nearby words fill out the range. Lean suggests muscle with little fat. Slender is slim with a touch more elegance, and is used more of women than men. Scrawny and bony are stronger than skinny and are plainly insulting. Thin sits in the middle and is the most neutral of all — if you want to describe a body without implying any verdict, thin or slim will serve you better than anything else here.
Frequently Asked Questions
Is calling someone skinny rude?
It can be. Skinny usually implies too thin, and many people hear it as a comment on their health or as criticism. Slim, slender or lean are safer if you mean it as praise.
Can I say "skinny chance"?
No — the idiom is slim chance. Slim carries the sense of small quantity; skinny does not work in that role.
What does "the skinny" mean?
The inside story or essential facts, as in "what's the skinny on the merger?" It is informal and mostly American, and is unrelated to body size.