A vowel whose time is that of short u , ū and the prolated ū , is called respectively hrasva short, dīrgha long and pluta prolated.,
The उ u having one matra or measure is short, having two measures is long, having three measures is pluta. This sutra defines the three kinds of vowels according to their matra. The letter ऊ u has been taken to illustrate the rule. The phrase हृस्वदीर्घप्लुतः is a Dvandva compound, in the Singular, and is exhibited in the masculine gender, contrary to the general rule 2.4.17.
The word kala means measure of time required for pronouncing a vowel.
As दधि 'curd', मधु 'honey'. Here इ and उ are short. कुमारी, गौरी, here ई is long. देवदत्ता३ अन्वास Devadatta! Here आ a is pluta or prolated.
These words are used in the following sutras: (1. 2. 47); 7.4.25; 8.2.82.,