1. What do the following words have in common?

MONTH
POISE
ALIAS
TIMER
NIECE
LUNGE

2. What do the following words have in common?

AWL
OWN
EDGE
OUGHT

HINTS:
1. It has to do with a single letter in each word.
2.The same two letters will change each word to a new one.

Answers:

1. Removing the middle letter of each word leaves a valid word:

MOTH/POSE/ALAS/TIER/NICE/LUNG

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

DRAWL / DROWN / DREDGE / DROUGHT