M
* Magnitude: Size, extent, or importance.
* Melancholy: A feeling of pensive sadness, typically with no obvious cause.
* Memory: The faculty of recalling past experiences.
* Mercy: Compassionate or lenient treatment of someone.
* Misery: A state of great suffering, unhappiness, or distress.
* Moderation: The quality of being reasonable and not extreme.
* Motivation: The reason or reasons one has for acting or behaving in a particular way.
* Mystery: Something that is difficult or impossible to understand or explain.
A
* Anger: A strong feeling of displeasure or hostility.
* Anxiety: A feeling of worry, nervousness, or unease.
* Awareness: Knowledge or perception of a situation or fact.
* Ambition: A strong desire to achieve something.
* Ability: The power or skill to do something.
* Acceptance: The act of consenting to something.
* Accuracy: The quality of being correct or precise.
* Adversity: A difficult or unpleasant situation.
* Affection: A feeling of fondness or love.
* Agreement: A mutual understanding or arrangement.
* Agitation: A state of worry or nervousness.
* Amusement: The state of being entertained.
* Analysis: The process of breaking down something into its parts.
* Anger: A strong feeling of displeasure or hostility.
* Annoyance: A feeling of irritation or displeasure.
* Applause: An expression of approval or appreciation, typically by clapping.
* Approval: The act of accepting or endorsing something.
* Argument: A disagreement, debate, or dispute.
* Art: The expression or application of human creative skill and imagination, typically in a visual form such as painting or sculpture.
This list provides a wide variety of abstract nouns, but it's far from exhaustive. There are many more abstract nouns starting with "m" and "a" that could be added.