Schwa and Halant are two opposite terms (concepts) in ĐevaNāgarī. Discussion about one is not complete without the other! Here we would discuss halant.
In ĐevaNāgarī, halant is a very important concept and an encoded character. But mostly it remains invisible! While writing ĐevaNāgarī on paper someone may rarely write it! [See FootNote]
In all the ĐevaNāgarī 'Full-form' consonants an inherent short vowel ‘अ’ is present. This short vowel is called 'schwa' ; and is represented as 'Ə' in IPA.
Full-form = Half-form (pure consonant) & Schwa
We type/use 'halant' immediately after a 'Full-form' consonant to remove schwa from that consonant.
Half-form = Full-form & Halant
In other words, when we type 'halant' after a 'Full-form' consonant, it changes the 'full-form' of that consonant to corresponding 'half-form'. This so called half-form is a 'pure' consonant. The halant may vanish when another consonant is typed and a conjunct/syllable is formed.
On mechanical typewriters, whatever once typed is final. So we have -
- both full-forms & half-forms of some consonants,
- only half-forms of some consonants,
- and only full-forms of remaining consonants.
The consonants whose only half-forms are represented (on keys) need a vertical stroke (representing schwa) to make them full-forms.
The consonants whose only full-forms are represented (on keys) need a halant to make them half-forms.
But electronic devices like computers and mobiles can convert a previously typed full-form to half-form if followed by halant. So there is no need to represent both the forms of any consonant on an electronic keyboard.
'Akār' (akar) is the vertical stroke that is present in most of the 'full-form' Akṣhar/s. When a 'full-form' is changed to its 'half-form' this 'Akār' is removed.
E.g. 'प' is the full-form of consonant 'pa' while 'प् ' ('p') is its half-form.
In क (ka) and फ (pha), Akār is present in the middle, which we can't remove. So corresponding half-forms become क् (k) and फ् (ph).
If Akār is not present in a full-form consonant then either we get a different half-form of that consonant or the halant becomes visible after that consonant.
E.g. 'ह' (ha) is the full-form while 'ह् ' (h) is its half-form.
Here we got a part of the full-form as the corresponding half-form.
E.g. 'ङ' is the full-form of the consonant 'n͘ga' or 'N͘Ga' while 'ङ्' is its half-form.
In other words -
- either halant removes the 'Akār' of the preceding consonant and vanishes,
- or changes the form of the preceding consonant by removing a part (from right hand side) of the preceding consonant and vanishes
- or remain visible after the consonant.
In most of the cases the half-form is a part of the corresponding full-form.
Even while composing ĐevaNāgarī text for letter-press of yesteryears, halant was/is required rarely.
While typing in electronic devices like computers and mobiles, halant is displayed temporarily till next consonant of the syllable is typed.
Mostly the halant is absorbed (not shown) in a syllable.
In ĐevaNāgarī, about 80% occurrence of the consonants are in their full-form.
It is simply called Hal (हल्). IMHO, Unicode standard erroneously used a word 'Virāma' to denote it!