Let T be a rooted tree with n nodes.

In the general case, let T be the subgroup of diagonal matrices.

Let T be the "time" whose axis has length continuum.

Let T be a regular chain in the polynomial ring R.

Let T be the year's last two digits.

Let T be the first time k copies of each coupon are collected.

Let T be a set consisting of all infinite sequences of 0s and 1s.

For example, let T be a torus, as shown on the right.

Let T be the number of different types of parts.

Let T be the time to access the memory.