1. (adjective) on or of upper floors of a building

• upstair

2. (adverb) on a floor above

• on a higher floor
• up the stairs

1. (noun) the part of a building above the ground floor

• part
• portion

1. (adjective) on or of upper floors of a building

• downstair
• downstairs

2. (adverb) on a floor above

• below
• down the stairs
• downstairs
• on a lower floor