Angles $1$ and $2$ in the diagram form a right angle, meaning their measures add up to $90^\circ$. Angles whose measures sum to $90^\circ$ are called complementary angles.

Answer: complementary

Would you like further clarification or details?

Here are 5 related questions:

1. What are the definitions of complementary and supplementary angles?
2. How can you determine whether two angles are complementary if one measure is known?
3. Can angles be complementary if they are not adjacent or do not form a right angle?
4. How do complementary angles relate to trigonometric functions?
5. How do you calculate one angle when the complementary angle is given?

Tip: Remember that complementary angles always sum to $90^\circ$, while supplementary angles sum to $180^\circ$.