What is the meaning of Proper_subset?

5-letter words containing

• 5-letter words containing r

• 5-letter words containing a

• 5-letter words containing l

• 5-letter words containing u

• 5-letter words containing i

5-letter words starting with

• 5-letter words starting with o

• 5-letter words starting with v

• 5-letter words starting with g

• 5-letter words starting with i

• 5-letter words starting with s

5-letter words in the middle

• 5-letter words in the middle r

• 5-letter words in the middle e

• 5-letter words in the middle v

• 5-letter words in the middle l

• 5-letter words in the middle s

5-letter words ending with

• 5-letter words ending with b

• 5-letter words ending with a

• 5-letter words ending with g

• 5-letter words ending with e

• 5-letter words ending with r

5-letter words excluding

• 5-letter words excluding l

• 5-letter words excluding p

• 5-letter words excluding s

• 5-letter words excluding k

• 5-letter words excluding r