Percent Sign

It means that many out of every hundred. 50% is half, 100% is all of it, 5% battery means your phone is nearly dead. "30% off" takes 30 of every 100 from the price, so a 50 price becomes 35.

Watch for one common trap: a change in percent is not a change in percentage points. If a rate goes from 2% to 3%, it rose by one percentage point, but by 50% of its old value. News and banks use both, and mixing them up makes a change sound much bigger or smaller.

In everyday chat, "100%" works as a word: "100%, let's go" means "absolutely". "110%" is a well-worn exaggeration for maximum effort.

Do you put a space before %?

In English, no: write 25%. Other languages differ. French, German, Spanish, Swedish, Danish, Norwegian and Finnish style guidance puts a space (ideally one that won't break across lines): 25 %. Turkish puts the sign first: %25. Follow the convention of the language you are writing in, and stay consistent within one text.

Why is % in my link?

It marks an encoded character, not a percentage. Web addresses can't contain spaces and some other characters, so they are encoded as % plus two hexadecimal digits: %20 is a space, %25 is the percent sign itself, and a letter like é takes several such groups. A link with "my%20photo" simply means "my photo". Programmers also meet % as the remainder operator: 7 % 3 gives 1.