how would you breakdown these words using root meanings, pretentious, evanescent, avarice, and astute.

Look them up in the dictionary; it will give you the root of the word.

Example from the on line Merriam Webster Dictionary:

pre·ten·tious
Pronunciation: \pri-ˈten(t)-shəs\
Function: adjective
Etymology: French prétentieux, from prétention pretension, from Medieval Latin pretention-, pretentio, from Latin praetendere
Date: 1832

GuruBlue is right. Any good dictionary will help you with these types of things.

Another good place is an etymological dictionary, such as http://www.etymonline.com/

To break down these words using root meanings, we can analyze the underlying roots or affixes that contribute to the meaning of each word.

1. Pretentious:
- The root word here is "pretend," which means to falsely present oneself or something as being impressive or important.
- The suffix "-ious" is added to "pretend" to form "pretentious," which means characterized by pretending, exaggerated self-importance, or making claims to be more impressive than it actually is.

2. Evanescent:
- The root word is "evanesce," derived from the Latin word "evanescere," which means to disappear gradually, vanish, or fade away.
- The suffix "-ent" is added to "evanesc" to form "evanescent," meaning something that is fleeting, temporary, or likely to disappear.

3. Avarice:
- The root word is "avar," derived from the Latin word "avaritia," meaning greed or excessive desire for wealth.
- The suffix "-ice" is added to "avar" to form "avarice," which refers to an extreme desire for wealth or material gain, often to the point of being greedy or unscrupulous.

4. Astute:
- The root word is "astus," derived from the Latin word "astutus," which means shrewd or clever.
- The suffix "-e" is added to "astu" to form "astute," indicating someone who is smart, perceptive, or sharp in their judgments or decisions.

By understanding the roots and affixes of these words, you can often infer their meanings even if you are encountering them for the first time.