What is a word?

[kyczawon]

Any sequence of lower-case or upper-case alphabetic characters is a word.

Does this mean that a word can be either a sequence of lower-case characters or a sequence of upper-case? Or a sequence of a mix of lower-case and upper-case characters?

Better safe than sorry hahaha

[mahudu97]

For example:
aaa
AAA
aAa

Will "aAa" be treated as a single word or three words of; 'a' , 'A' and 'a'.

[m8pple]

Yup, this came up in discussion in lab a few times.

The English description is (as much as possible) written to match the regular expressions,
and your question actually mostly answers the question. So you say it could be:

a word can be either a sequence of lower-case characters or a sequence of upper-case characters

or

a sequence of a mix of lower-case and upper-case characters

The way that you have tried to clarify those is actually trying to indicate some idea of
precedence or clustering. So I would interpret those as:

(a sequence of lower-case characters) or ( a sequence of upper-case characters)

or

a sequence of ( lower-case and upper-case characters )

These are now clearly two different patterns.

If we now take the words in the spec:

sequence of lower-case or upper-case alphabetic characters

we could try playing with the bracketing (or more technically, precedence).

So one version is:

(sequence of lower-case) or (upper-case alphabetic characters )

versus:

sequence of (lower-case or upper-case alphabetic characters )

I admit that there might be a cultural/ bias here (native language
does bias interpretation) but as an English speaker the first version is
weird, while the second one makes sense.

So I would argue that in English the operator or binds higher
than (or has higher precedence than) the sequence of operator.

This is actually at the crux of grammars and derivations - how should the
English version (or any human language) be derived (grouped)?

Eventually this leads to derivation problems like the famous
(possibly apocryphal) newspaper headline Prostitutes Appeal to Pope

In formal grammars we will aim for just one derivation an meaning.

[babba16]

Sorry my comprehension skills are lacking.
So just to clarify
aAa will be treated as one word not three separate ones

[mahudu97]

@babba16 "aAa" will be treated as one word.