A consonant cluster is a group of consecutive consonants with no vowel sounds between them. Consonant clusters are common in Sanskrit, so they are common when we write Sanskrit in Devanagari.
First, here are the two clusters you absolutely must know:
Why must we know these two clusters? These two clusters do not resemble their original consonants at all, so we cannot guess what sounds they represent. That is why we must learn them separately.
Now, let's consider the other consonant clusters. Notice that most Devanagari consonants have a single vertical line running from top to bottom. Usually, this line is on the right side of the consonant:
In many consonant clusters, the first consonant loses this line and attaches to the consonant that follows it:
If ra is the first consonant, we simply add a small hook to the top of the second:
If ra is second, we add a small tick to the first consonant:
But consonants with a “hoop” shape (like ट, ठ, and ढ) use a different symbol instead:
If na is second, we write it in the same way as ra:
If ha or da is first and ya or ma is second, we get these combinations:
If śa is first, it becomes a smaller form that sits on top of the second consonant:
If ṣa is first, it often stacks vertically on top of the consonants that follow it:
Voiced aspirated consonants that follow da usually “dangle” off the bottom of the da:
ta combines in various ways that are hard to predict:
And if three or more consonants are in a cluster, we sometimes get more complex combinations: