Is attitude and aptitude words that were derived from the same source word are an example of a doublet?

You are very close! Attitude and aptitude are not a doublet, but they are related words that share a common origin.

Here's why:

* Doublets are pairs of words in a language that have the same origin but have diverged in meaning and spelling due to separate linguistic developments.

* Attitude and aptitude share the same Latin root, *aptus*, meaning "fit, suitable, ready."

However, they are not considered a doublet because their meanings are distinct:

* Attitude refers to a mental position or feeling about something.

* Aptitude refers to a natural ability or talent.

Therefore, attitude and aptitude are cognates, not doublets. Cognates are words that have a common origin but have evolved into different meanings and spellings over time.