1. What do the following words have in common?

SEAS
LESS
TEND
CART

2. What do the following words have in common?

CASH
DEAL
VALID
HINT
FIRM

3. What do the following words have in common?

ASH
AND
HAT
HERE
OVEN

HINTS:
1. The same two letters, in the same position, will change each word into a new one.
2.  First hint - The first letter of each word has to be dropped.
2.  Second hint -  The first letter has to be replaced by the same three letters.
3. The same letter, in the same position, will change each word into a new one.

Answers:

1. Adding the letters ON to each word will create new words:

SEASON / LESSON / TENDON / CARTON

2. Replacing the first letter of each word with SQU will create new words:

SQUASH / SQUEAL / SQUALID / SQUINT / SQUIRM

3. Each word can be preceded by W to create a new word:

WASH / WAND / WHAT / WHERE / WOVEN