Tertiary can have different meanings depending on the context. Here are some definitions:

• Tertiary education: This refers to the educational level following the completion of secondary education. It includes universities, trade schools, colleges, and vocational schools. Tertiary education generally culminates in the receipt of certificates, diplomas, or academic degrees.

• Of third rank, importance, or value: This is the most common meaning of tertiary. For example, a tertiary color is a color made by mixing two secondary colors.

• Relating to a third level or stage: This meaning is similar to the previous one. For example, a tertiary consumer is an animal that eats secondary consumers, which in turn eat primary consumers.

• Containing a carbon atom united to three other carbon atoms: This is a chemical meaning of tertiary. For example, a tertiary alcohol is an alcohol in which the carbon atom that carries the hydroxyl group is attached to three other carbon atoms.

• Formed by replacement of three atoms or groups: This is another chemical meaning of tertiary. For example, a tertiary amine is an amine in which three hydrogen atoms of the ammonia molecule have been replaced by organic groups.

In summary, tertiary can refer to education, rank, level, or chemistry, depending on the context.