What do the following words have in common?

LAM
DING
TIME
ROCK

2. What do the following words have in common?

GLOSS
VISION
ELEMENT
COMMENT

3. What do the following words have in common?

YOUTH
THEME
USHER
SHEIK
ITALICS
MEDIUM
WEEVIL

HINTS:
1. Each word can be preceded by the same three-letter word.
2. The same three letters will change each word into a new one.
3. Each word hides a different, but related, word.

Answers:

1. Each word can be preceded by BED:

BEDLAM / BEDDING / BEDTIME / BEDROCK

2. Each word can be followed by ARY.

GLOSSARY 
VISIONARY 
ELEMENTARY 
COMMENTARY

3. The first two, three, or four letters of each word are pronouns:

YOUth
THEMe
USher
SHEik
ITalics
MEdium
WEevil