When something is useful, convenient or helpful we can say it is handy.
“An iPad is a handy thing to have when you travel.”
“My apartment is handy for school.” – My apartment is near to school.
“She’s very handy with a paintbrush” – She’s good at painting.
Handy is also used in the idiom come in handy meaning to be useful e.g. “Don't throw that map away, it might come in handy.”
Sign language is a system of communication using visual gestures and hand signs, as used by deaf people (people who cannot hear).
