Undershirt vs. Onesie — What's the Difference?

An undershirt in American English (vest in British and Indian English, or singlet in Australia and New Zealand), is an article of underwear worn underneath a dress shirt (or sometimes T-shirt) intended to protect it from body sweat and odors. It can have short sleeves (T-shirt) or be sleeveless (A-shirt).

A loose-fitting one-piece leisure garment covering the torso and legs

An upper undergarment, typically having short or no sleeves, worn next to the skin under a shirt.

A one-piece close-fitting lightweight garment worn by a young child, usually having sleeves but leaving the legs uncovered and fastening with press studs at the crotch.

An undergarment worn beneath a shirt, often collarless and sleeveless.

Name given to a number of one-piece attires

A shirt worn next the skin, under another shirt; - called also undervest.

(US) A one-piece garment for an infant or small child, generally worn over a diaper.

A collarless men's undergarment for the upper part of the body

One-piece adult loungewear jumpsuit.

One-piece fashionable streetwear worn mostly by teenagers.