Meaning is related to Sign. Sign is related to Nod. Nod is related to Agree. Agree is related to Mutual. 
Dock is a type of Herb. Carrot is a type of Herb. 
Meaning <--RelatedTo--> Sign <--RelatedTo--> Nod <--RelatedTo--> Agree <--RelatedTo--> Mutual 
Dock --IsA--> Herb <--IsA-- Carrot 