1. impulsive and unpredictable; subject to whim
capricious
ADJECTIVE
impulsive and unpredictable; subject to whim

2. cloister
VERB
To seclude or shut up in

3. lack of similarity or equality; inequality; difference
disparity
NOUN
lack of similarity or equality; inequality; difference

4. capacity for producing a desired result or effect; effectiveness
efficacy
NOUN
capacity for producing a desired result or effect; effectiveness

5. a letter, esp. a formal or didactic one
epistle
NOUN
a letter, esp. a formal or didactic one

6. idiosyncrasy
NOUN
a mode of behavior or way of thought peculiar to an individual; a distinctive or peculiar feature or characteristic

7. a moving force; impulse; stimulus
impetus
NOUN
a moving force; impulse; stimulus

8. moribund
ADJECTIVE
in a dying state; near death; on the verge of extinction or termination

9. reticent
ADJECTIVE
disposed to be silent or not to speak freely; reluctant , reserved, or restrained

10. to waver in mind or opinion; to be indecisive or irresolute
vacillate
VERB
to waver in mind or opinion; to be indecisive or irresolute