The languages for which the Devanagari script is used regularly employ consonant clusters such as [kʃ], [pr], [sv] and [tj], both at the beginning of and within words. To represent these in writing, the inherent vowel contained in every consonant letter must be deleted somehow. To this end, consonant ligatures (generally called conjuncts when referring to Indic scripts) number in the hundreds. Some consonants, particularly those with a rounded bottom such as ड da, cannot be written with a ligated conjunct; these are modified with a halant symbol to indicate that the vowel has been muted. So the sequence dla would be written with two distinct letters: ड्ल.

Most consonant letters have a 'half' form which enables them to represent consonant clusters without the use of halant. The half form tends to look similar to the 'full' form of the letter, but without the vertical stem which is graphically and historically related to the a vowel letter. This 'half' form can join to the left of a 'full' consonant letter so that they can be pronounced in sequence. For example, the letters त ta and स sa can combine to produce त्स [tsə].

Some letters do not join horizontally in this way, but instead stack vertically. This particularly applies in cases where the first letter does not have a vertical stem, such as ट and ठ ṭh which stack to produce the conjunct ट्ठ [ʈʈhə]. Some combinations are attested in both horizontal and vertical arrangements, such as kka (क+क), which can be written either क्क or क्क.

The final class of consonant clusters are those which are represented using a new letter, which is not so easily decomposable into the shapes of the individual letters comprising it. Commonly used examples of these are:

ka + ष ṣa = क्ष
ja + ञ ñ = ज्ञ
ta + त ta = त्त
ta + र ra = त्र

The use or non-use of a ligature is optional in some words. For example, [bɪlkul] ('entirely') can be written with the l+k conjunct ल्क or with the full forms of both letters (probably using a halant below the l) without changing the pronunciation or the meaning of the word. In the case of other words, the use or non-use of a conjunct is determined by the word's morphology and changes its meaning. For example, [kərta], when written with the r+t conjunct represents the Hindi word for 'doer/maker' कर्ता, but when written with a full r and a full t, the break in letters represents a morpheme break between the root of the verb 'to do' [kər-], and the imperfect participle masculine ending [-ta], so the word करता means '(he) does'. Note that this means the orthography does not necessarily represent syllables in a phonological sense; both senses of [kərta] contain the syllables kər+ta but the syllable break is not represented when using a conjunct.