Slave can be used for Labor. Labor is related to Birth. Birth is part of Life. 
Activity is related to Call. Call is the opposite of Whisper. Whisper is related to Soft. 
Slave --UsedFor--> Labor <--RelatedTo--> Birth --PartOf--> Life 
Activity <--RelatedTo--> Call <--Antonym--> Whisper <--RelatedTo--> Soft 