1. What do the following words have in common?

ILL
IMP
INK

2. What do the following words have in common?

DRESS
VERSE
VENT
DING
RIFT

HINTS:
1. The same three letters, in the same position, will change each word into a new one.
2. The same two letters, in the same position, will change each word into a new one.

Answers:

1. Each word can be preceded by SHR to make a new word:

SHRILL / SHRIMP /  SHRINK

2. Each word can be preceded by AD to make a new word:

ADDRESS / ADVERSE / ADVENT / ADDING / ADRIFT