La is the third of the four semivowels, the dental liquid, and the phoneticians pair it with the vocalic l that stands among the vowels. It holds the third place in the block, after ra and before va, and the four are recited together as a unit in the traditional teaching of the table.
Sanskrit separates it firmly from ra, and a number of word pairs turn on nothing else. The separation is nonetheless historically recent in part: the two interchange in the older language and in the Prakrits often enough that etymologies cross freely between them, and a root can appear with either liquid in different periods and regions.
The letter is common in the vocabulary and enters conjuncts freely, taking a reduced form beneath the consonant it follows. Like the other semivowels it also participates in the rules that convert a vowel to its consonantal counterpart across a word boundary.
In the East Asian material it has no separate liturgical role of the kind ra and va acquired, which is a reminder that the five seed syllables of the elements are a selection made for a purpose rather than a summary of the table. The letters chosen for that scheme were chosen; the others were not passed over for any fault.