To move slightly or gradually

• shift
• variety
• deplete
• peak

To use up your supply of something

• variety
• delete
• deplete
• shift

The most important thing you have to achieve

• peak
• extract
• priority
• substitue

Extremely large in size and amount

• essential
• priority
• enormous
• deplete

A period of time in history

• era
• ear
• are
• extract

The use of one thing instead of a different thing

• essential
• substitue
• extract
• variety

Absolutely necessary

• priority
• variety
• essential
• enormous

The highest amount or value of something

• era
• peak
• extract
• substitue

To remove a thing or substance from a place

• extract
• era
• essential
• enormous

A number of different kinds of the same thing

• deplete
• variety
• shift
• essential