godan verb (-su), transitive verb
Specifically for arithmetic addition. Used with numbers, amounts, or mathematical expressions.
5に3を足すと8になる。
If you add 3 to 5, you get 8.
消費税を足した金額を計算
Please calculate the amount with consumption tax added.
godan verb (-su), transitive verb
add (something); top up; supplement
General sense of adding something extra to what already exists: ingredients, liquid, items, etc. Often used when topping up or supplementing.
味が薄いので、塩を少し足した。
The flavor was weak, so I added a little salt.
コーヒーが少なくなったので、お湯を足しておいた。
The coffee was running low, so I topped it up with hot water.
godan verb (-su), transitive verb
take care of (business); do (one's business)
Used in the fixed expression 用を足す, meaning to run an errand or, euphemistically, to relieve oneself. Not freely productive outside this phrase.
See also: 用を足す
ちょっとコンビニで用を足してくる。
I'll just go run a quick errand at the convenience store.
すみません、ちょっと用を足してきます。
Excuse me, I need to go take care of something (euphemism for using the restroom).