I'll start with weird etymology trivia, just for fun.
Etymological doublets? Triplets? What about sextuplets, to make the Nakano sisters jealous? Latin ⟨macula⟩ /'ma:kula/ "stain" yielded at least the following words in Portuguese:
⟨mancha⟩ /'maN.ʃa/ (stain)
Inherited word, for what you'd use when you drop ketchup on your white shirt. Likely the result of
- /'ma:kula/→
- */'ma.kla/ (Vulgar Latin)→
- */'ma.gla/→
- */'ma.tʎa/ (likely areal change, as Spanish also underwent it)→
- */'maN.tʎa/ (progressive nasalisation; /N/ stands for the vowel nasalisation, often the language handles it as its own thing) →
- /'maN.tʃa/ (Galician-Portuguese times, with a few Portuguese dialects like Trasmontano still keeping /tʃ/) →
- /'maN.ʃa/ (phonemic form for most modern speakers)
⟨malha⟩ /'ma.ʎa/ (fur stain/spot)
It's how you'd call those "stains" on a spotted cow (vaca malhada) or a dog (cachorro malhado).
The progressive nasalisation that I mentioned for ⟨mancha⟩ is highly erratic in Portuguese, even if it's still productive for some people. That likely allowed the forms */'ma.tʎa/ and */'maN.tʎa/ to coexist for until outliving that odd Ibero-Romance */tʎ/.
However, the outcome of /tʎ/ depends on the environment - it affricates to /tʃ/ after consonant (as in ⟨mancha⟩), but simplifies to /ʎ/ in intervocalic position (as in ⟨malha⟩).
⟨mangra⟩ /'maN.gɾa/ (archaic word for mildew)
This word is clearly related to both above, but I'm not sure if it's an extremely early reborrowing or a dialectal form. Either way, it shows the same /kul/→*/kl/→*/gl/ sequence of sound changes as both above, and then instead of /Cl/→/tʎ/ it goes with /Cl/→/Cɾ/ - rhotacism, historically common in the language, and still productive for some speakers.
⟨mágoa⟩ /'ma.go.a/~/'ma.gwa/ (grief, sorrow)
Semi-erudite borrowing, for things that stain your feelings.
The word was reborrowed late enough to not undergo /kul/→*/gl/, but early enough to see Portuguese intervocalic lenition of /l/→Ø; see ⟨colorem⟩→⟨cor⟩ colour, ⟨calentem⟩→⟨caente⟩→⟨quente⟩ hot for examples of the same phenomenon.
⟨mácula⟩ /'ma.ku.la/ (stain, character flaw)
Erudite borrowing, pronounced somewhat the same as in Latin... well, if you disregard the lack of vowel length and that the vowel qualities are a bit off.
It's a bit of a posh word. Mostly used for abstract "stains", or in medical terms.
⟨malha⟩ /'ma.ʎa/ (mesh, [chain]mail)
No, I didn't list this word twice - it's likely an etymological doublet with its own homonym.
Likely borrowed laterally from French ⟨maille⟩. Likely old, since French eventually underwent /ʎ/→/j/.