[Meaning] what is unpurified.[1]
Or what has nothing more than the rest.
'Common' has a fourfold application: (i) what is divisible into parts, such as the earth obtained by allotment; (ii) what is indivisible, [such as] what is taken for common usage; (iii) what is appropriated to oneself with anticipation and is referred to what is common, such as a place in a theater or in a bath-house; (iv) what indivisibly is set before with regard to the common and the same conception, such as the voice of the herald.[2]
The Father, the Son, and the Holy Spirit, as well as the Scriptures and the supramundane powers, both the sun and the moon, and all the chorus of stars and the air itself are totalities thoroughly common and indivisible. Earth and water, gold and silver, and every metallic natural reality and woody matter are common, but, nevertheless, they have come to be divisible because of the desire for gain. Virginity, celibacy, priesthood, and the rest of things belonging to God are graces of such kind that are neither common nor divisible, for they do not belong to the part of common and divisible things.[3]