The sequence 3, 7, 11, 15 illustrates an arithmetical progression with common difference 4.

The professor assigned several problems involving arithmetical progressions to help students recognize patterns.

Linguists documented several progressive assimilations in the regional dialect during the twentieth century.

In our phonetics seminar, we analyzed progressive assimilation and observed how a consonant becomes more like the preceding sound.

The professor used several harmonic progressions as examples during the lecture.

The mathematician explained how a harmonic progression is formed when the reciprocals of its terms make an arithmetic progression.

The astronomer's notes showed a surprising geometrical progression in the spacing of the rings.

In her lecture, she compared the convergence of different geometrical progressions to illustrate the concept.

Many economists argue that a progressive tax encourages social equity without stifling entrepreneurship.

In this grammar exercise, mark each verb as either progressive or non-progressive.