Ignore is the opposite of Observe. Monitor is a type of Observe. Monitor is a synonym of Oversee. 
Sand is a type of Soil. you are likely to find Sand in/at/on Concrete. Concrete is related to Steel. you are likely to find Steel in/at/on Mill. 
Ignore <--Antonym--> Observe <--IsA-- Monitor <--Synonym--> Oversee 
Soil <--IsA-- Sand --AtLocation--> Concrete <--RelatedTo--> Steel --AtLocation--> Mill 