In this example we want a name, so we insist that it contains at least one capital letter [A-Z]
We could also insist that the characters are all lower case using matches and [a-z ]+
Note the space is really important if you want to have more than 1 word.
Perhaps you are concerned about people using dogs rather than dog. In many cases both might be correct. Well you can sort that quickly using a maximum length.
You can also use numbers and this can be a great way to not only test maths questions, but also to give a large range of options with a multiple choice diagram,
For example you can easily ask test questions about this heart with a few simple short answer questions rather than do a dropdown from 1-8 or multiple choice.
If you'd like to do more complex regex expresions there's a great site to help you: https://regexr.com/ Please note that there are dialects, so not all regex you find on the internet will work with Google forms.