Regular expression for 8 to 10 letter words

Question

I need a regular expression that matches either 8 letter words ending in "tion" or 10 letter words ending in "able".

Here is what I came up with, but for some reason http://regex101.com tells me there are no matches when I try to match a string.

My idea is as follows:

([a-z]{4}^\btion\b|[a-z]{6}^\bable\b)

Link to regex101 - Here

Answer 1

Try this one:

\b([a-z]{4}tion|[a-z]{6}able)\b

Demo

You use ^\b between the variable section (e.g. [a-z]{4}) and constant postfix (e.g. tion) and that breaks the match. ^ means "beginning of the string (or a line)" and \b means "word boundary". Using it together makes little sense, as beginning of the string is always a word boundary.