Definitions of particular:

• noun:   a fact about some part (as opposed to general)

  Example: "He always reasons from the particular to the general"

• noun:   a small part that can be considered separately from the whole
• adjective:   first and most important

  Example: "She gets special (or particular) satisfaction from her volunteer work"

• adjective:   exacting especially about details

  Example: "Very particular about how her food was prepared"