The term ideal has multiple meanings:

In mathematics

• ideals are special subsets of a ring considered in abstract algebra.
• ideals appear in order theory and are a special kind of lower sets of an order.

In physics

• The ideal gas law which governs the pressure of an ideal gas.
• An ideal transformer is a transformer having zero resistance and perfect magnetic threading.
• A thought experiment, sometimes called an ideal experiment.

Other

• Ideal is the name of a late 1990s/early 2000s American R&B singing group.
• Ideal is the name of a toy company.