Unnatural describes something that doesn't happen or exist in nature, or something that seems forced, artificial, or wrong in some way. When scientists create a substance in a laboratory that never existed before in nature, like certain plastics or chemicals, they might call it unnatural. When someone smiles for a photo but the smile looks stiff and fake rather than genuine and relaxed, we say it looks unnatural.

The word often points to a contrast with what's normal or expected. An unnatural silence in a usually noisy cafeteria feels eerie and strange. An unnatural posture, like standing with your shoulders hunched up by your ears, feels uncomfortable because bodies aren't meant to hold that position.

Sometimes people use “unnatural” to criticize things they're uncomfortable with, but be careful: just because something is uncommon doesn't make it unnatural. Left-handedness used to be called unnatural, but it occurs naturally in about 10% of people. The word works best when describing things that truly don't occur in nature (like some food colorings) or behaviors that feel genuinely forced or fake (like an unnatural laugh that sounds rehearsed rather than spontaneous).

The opposite of unnatural is natural: occurring in nature, or flowing easily and genuinely.