Envelopes

The teacher gave the students envelopes for their writing assignments, such as word count and theme.

The government agency required that all documents be submitted in sealed envelopes.

The geologist used the envelopes to map the rock formations in the area.

The athlete knows his body's envelopes and how much he can push himself during a race.

The stack of envelopes on her desk contained bills, letters, and junk mail.

The doctor explained the envelopes within which a medicine can be used safely.