Warning: this is not a catechetical post.
English is just the best; it's so rich in words. Not only do we have oodles of 'regular' English words such as chicken, deer, lawyer, pig, and cow, but also thousands of French words such as poultry, venison, attorney, pork, and beef. And words from India such as shampoo, bungalow, ketchup, punch, khaki, and jungle. Not to mention several thousand more loanwords from all over the planet. I will not mention them. But English isn't just a mix of vocabularies: it's also a mix of grammars.
One of the many charms (or aggravations) of English is its plurals. The easiest don't even require a change: deer, fish, moose. Other easy ones all end in s: cats, dogs. Fussier ones take an s but have a consonant change: leaf/leaves; house/houses; mouth/mouths. The oddest (and oldest) require a vowel change to make the plural: geese, men, mice, lice, brethren, cistern (kidding), and my favorite, women. Women is my favorite because both vowels change to make the plural. German, one of English's cousins, requires vowel changes even more than English does. How nice that in German the change may be indicated by an umlaut, those two dots that occasionally appear over its vowels. Like so: Mötley Crüe. Just kidding. I mean like so: ä, ö, ü. Thus in German there is one Buch/ book, and two Büche; one Hand, two Hände. The umlauted vowels sound different. If we used such marks, we might spell particular plurals like this: man/ män; woman/ wömän; and goose/ göse. English umlauts all sorts of words, not just nouns (e.g., sink/sank/sunk); but doesn't ever use the marks.
Now Anglophones learning German often don't want to worry about the umlauts; they're content to show the plain vowels. After all, English don't need no stinkin' umlauts to indicate vowel change...but failure to use the umlaut can radically change a word's meaning.
Here's a little Anglo-Deutsch example which visually makes the point.
With an Umlaut:
Without an Umlaut:
Which example is your favorite? Well, probably neither one...but you get the, uh, point.