Vaisesika Sūtra 2.1.14

वायोर्वायुसम्मूर्च्छनं नानात्वे लिङ्गम् ॥१४॥

vāyorvāyusammūrcchanaṁ nānātve liṅgam ॥14॥

[वायोः वायुसम्मूर्च्छनं नानात्वे लिङ्गम्॥
vāyoḥ = of Air; vāyusammūrcchanaṁ = merging with Air; nānātve = "manifoldness"; liṅgam = is the distinguishing mark;॥]

As Air gets mixed with Air, multiplicity is its distinguishing mark.

Air cannot be distinguished and counted like other physical objects.