Hash sign (#)
The hash sign (#) is two upright strokes crossed by two horizontal ones. It can stand for “number” (#1), is called the pound sign in the US, and on social media turns a word into a hashtag that groups posts on one topic.
Easily confused with
How to read it
Unicode names it NUMBER SIGN (U+0023) and lists its other names: pound sign (for weight), hashtag, hash, crosshatch and octothorpe. The American Heritage Dictionary separates them. As the number sign, # represents the word “number”. As the pound sign, it is the symbol for a pound as a unit of weight, while the same name also covers £ for the pound sterling. “Hash” it marks as chiefly British. Octothorpe, the dictionary says, was coined in the 1960s by researchers at Bell Telephone Laboratories: octo- probably for the eight ends of the lines, and -thorpe perhaps from thorp, a village among fields, or after the athlete Jim Thorpe. A hashtag, in its definition, is a searchable keyword prefixed with #, marking what a post is about. The at sign does a different job beside it, addressing a person rather than tagging a topic.
Also searched as: #, hash sign meaning, hash sign symbol, hashtag symbol, number sign, pound sign #.
Look-alikes
The musical sharp sign ♯ (U+266F) looks much the same. Unicode notes that ♯, not #, is the character to use for a musical sharp.
More punctuation and typographic symbols
Browse symbols drawn with lines.
Sources
- C0 Controls and Basic Latin: Range 0000–007F (code chart), The Unicode Standard, Version 18.0, Unicode Consortium, Basic Latin, 0023
- number sign (American Heritage Dictionary entry), The American Heritage Dictionary of the English Language, Fifth Edition, HarperCollins Publishers, number sign, n.
- pound sign (American Heritage Dictionary entry), The American Heritage Dictionary of the English Language, Fifth Edition, HarperCollins Publishers, pound sign, n.
- hash (American Heritage Dictionary entry), The American Heritage Dictionary of the English Language, Fifth Edition, HarperCollins Publishers, hash, n. (third entry)
- octothorpe (American Heritage Dictionary entry), The American Heritage Dictionary of the English Language, Fifth Edition, HarperCollins Publishers, octothorpe, n.
- hashtag (American Heritage Dictionary entry), The American Heritage Dictionary of the English Language, Fifth Edition, HarperCollins Publishers, hashtag, n.
- #OriginStory, Carnegie Mellon University homepage story, summer 2014, Carnegie Mellon University, Story text
- Groups for Twitter; or A Proposal for Twitter Tag Channels, Chris Messina, 25 August 2007, FactoryCity (Chris Messina’s blog), Post text
Last reviewed October 1, 2026 by Rory Hansen. How we research