I have used this regex to match a valid sentence:

It serves the purpose to validate a sentence – (by definition)

1. starts with Capital letter(s)
2. no punctuations in the middle of sentence, and
3. it ends with one or more of the punctuations. (eg. ?!)
   (because the 2nd part is very similar with 3rd part, except negation)

The question I have – is there a way to make it more concise?

/[A-Z]+[^\.?!][\.?!]+/  

# will match all the sentences:
s1 =  "A boy likes to read books."
s2 = "ABBA is one of the best musical bands."
s3 =  "Are you kidding me?!" 

# but not these sentences:
s4 = "City leaders allocated the first half of the ARPA funding to a series of initiatives,"
s5 = "will you abide the new law?"         

>Solution :

Here are a few way:

• You don’t need to escape the dot in character classes, so [\.] is the same as [.]
• You only need 1 capital letter at the start (can remove the plus)
• You can use reluctant quantifier .*? (as little as possible)

This should work:

[A-Z].*?[.?!]+

Consider removing the +, unless you really need to match sentences that end with ?? or ?! or !!! etc.