The word "सु+आगत" (su+aagat) undergoes a sandhi transformation in Sanskrit. Sandhi is a process of combining two words, and certain changes occur at the junction of the two words.
In this case, the combination of "su" and "aagat" results in the sandhi form "स्वागत" (swagat). Here, the "u" of "su" changes to "v" when combined with the following vowel "a" in "aagat". This is a common sandhi rule in Sanskrit.
So, "सुआगत" becomes "स्वागत" after sandhi.
