1. "Not" or "Without": This is the most frequent use of the prefix "a". It indicates the absence or lack of something.
* Apolitical: Not interested in or concerned with politics.
* Amorphous: Without a definite form or shape.
* Asleep: In a state of sleep, not awake.
* Atheist: A person who does not believe in God.
2. "On" or "In" (related to place or direction): This meaning is less common but still important.
* Aboard: On a ship, train, airplane, etc.
* Ashore: On the shore.
* Afield: In the field.
3. "To" or "Toward": This is another less common meaning, used to indicate direction or movement.
* Abroad: To or in a foreign country.
* Askew: Turned or twisted to one side.
4. "Of" or "Having": In some words, "a" indicates possession or connection to something.
* Afraid: Having fear.
* Alive: Having life.
* Ashamed: Having a feeling of shame.
It's important to note that the meaning of "a" can sometimes be subtle and dependent on context. If you're unsure about the meaning in a specific word, it's best to consult a dictionary.