AptApt means suited to the purpose or the occasion. If something is apt it is apropos or fits the situation or purpose well.
Ex: His solemn words were apt for the occasion, since everyone felt very sad about the cancellation of the trip due to Hank's circumstances.
Ex: The short amount of time we had to see the museum proved apt, since so many of the exhibits were closed.
Apt can also mean likely, disposed, or given to. Here, the word is used with to, as in apt to argue.
Ex: As both sisters and best friends, Madeline and Jane are apt to agree, but they do have a difference of opinion on occasion.
Ex: I am more apt to choose a history book than any other subject when I go to a large bookshop, although I will occasionally choose a cookbook.
AppropriateAppropriate means proper, fitting, meeting the purpose or occasion well, suited for the purpose. When appropriate is used as a verb, there the last syllable is pronounced with a long a sound and the word means to take something belonging to another and use it without permission, as in a policeman appropriating a vehicle during an emergency.
Ex: Bill searched for the appropriate words to express his sympathy for his friend, but he found it difficult to say anything at all.
Ex: This is the third time in two months that someone has seen fit to appropriate Cindy's stapler for other purposes and she is becoming very frustrated with the lack of respect for property here.
Inappropriate means not fitting or proper for the occasion, not well-suited for the purpose. If something is inappropriate, it does not fit the circumstances well.
Ex: Jake felt that his clothes, despite the protests of his companions, were inappropriate to attend a Broadway show, and he determined to buy a new outfit for the occasion.
Ex: While some fashion rules have changed over time, in most circles it is still considered inappropriate to wear white to a wedding.