ABCs refers to the alphabet, the 26 letters that form the building blocks of written English. When young children learn their ABCs, they're memorizing the sequence from A to Z, often through the famous alphabet song that starts “A, B, C, D, E, F, G...”

Parents and teachers use it when talking about basic literacy: “She's learning her ABCs” means a child is starting to recognize and name letters.

The phrase also means the most basic, fundamental parts of any subject. When a coach teaches you the ABCs of basketball, they mean essential skills like dribbling, passing, and shooting. A book about the ABCs of cooking would cover basics like measuring ingredients and using kitchen tools safely. In science class, understanding the ABCs of the scientific method means grasping the core steps: observation, hypothesis, experiment, and conclusion.

When someone says you need to learn the ABCs of something, they mean you should master the fundamentals before moving to advanced topics. You can't write poetry before learning your ABCs, just like you can't compose symphonies before understanding basic musical notes.