1. located on or relating to a lower floor of a building, especially the ground floor
Usage: often used in British English; more commonly seen in the plural form 'downstairs'

1. to or on a lower floor of a building
Usage: often used in the plural form 'downstairs'; less common as singular

Examples

• The downstair bathroom is being renovated this month.
• She went downstair to answer the door.
• The downstair rooms are cooler in summer.
• He heard voices coming from downstair.
• We use the downstair kitchen for cooking.
• The guests are waiting downstair in the living room.