I am new to the German language and my knowledge is just starting to expand out. I went through all the rules and guides that are part of the grammar, but I can't wrap my head around why the noun "Baum" [English: tree] is in masculine form - der Baum and not das Baum, as this noun gender identification guide suggests.
Here are the noun endings for the neuter form: -chen, -lein, -icht, -il, -it, -ma, -ment, -tel, -tum, -um.
The rules don't always apply, esp. when the endings are not morphological. And -um is neuter only if the noun comes from Latin that way (Individuum, Museum). But Baum is "natively" German; apart from that, it is B-au-m with diphthong, not Ba-um. Similar counterexample: der Schaum, der Traum, der Flaum, der Zaum.
(Other endings have their exceptions as well, e.g., die Pflicht, der Stil, die Oma)
-us is not the nominative singular of the O declination. (omnibus is ablative plural of omnium.)
Commented
Oct 10, 2020 at 7:40
There are much more exceptions from German gender rules than there are rules. The best way to learn German genders is like German native speakers do: Learn for each noun separately which gender it has.
Toddlers growing up in a German speaking world do not learn the genders of the nouns by memorizing such rules.
One of the first words a child learns is "Mama" (Engl.: mum or mom) and children learn, that people say "die Mama", so they learn, that this specific word is female (although it ends in -ma and violated one of your rules). Then "die Oma" (grandma) and so on.
Take these rules as first guidelines. They can help you in more than 90 % of all cases, but be aware, that all of them have really many exceptions.
And the rule for -um does not apply to der Baum, becaue Baum does not end in -um. It ends in -aum and au is a diphthong that under no circumstances can be separated. This is like in the English word "loud". The diphthong is the same, just the letters are different, but also in English you can't separate o from u in a word like loud.
In a similar way to how we have spelling bees in English, German kids play "guess the gender" on words. As with English spelling, there are some basic rules, but there are many exceptions.
And even, some of the rules don't make much sense. Consider the suffix "-chen", for instance. Kaninchen, or maedchen. The rule is that regardless of the actual gender, anything with the suffix "-chen" becomes neuter. So rabbits and girls are both neuter. Go figure.
In short, the only real way is to learn them one at a time. And as a non-native speaker, expect to get things wrong fairly often on all those exceptions. The good news is that since German kids also get this wrong (because they're still learning), Germans are tolerant of this and will still understand what you mean.
I think the lists on that page are a bit too long. I believe such lists can be useful as rules of thumb for really common endings, or for endings with really really few exceptions. This would reduce the list to -chen, -lein, -ment, -tum, -um.
I also think these lists are more useful for somewhat advanced learners. If you are just beginning to learn the language, it is probably enough to just keep in mind that words with certain endings can have a tendency (though sometimes a very strong tendency) towards a certain gender. And then try to remember those endings once you come across them.
E.g. the female endings -ung and -heit will come quite early because they appear in really common words (die Ordnung, die Krankheit etc) and -nis (die Finsternis) and -tum (das Eigentum) will come quite a bit later. IMHO from that list probably only -chen and -um (the latter only as a rule of thumb and for words of latin origin) are useful to keep in mind for beginners.
I honestly fail to see the usefulness of remembering the endings -icht, -il, -it, -ma, -tel. Either because there are too few words that have these endings to make it worth learning such a rule (-il, -icht, -ma) or because there are too many exceptions:
The rules don’t actually apply in a general case like the way you have phrased it implies. These are all* cases of suffixes which are used to form derivatives in either German or whatever language the word comes from (usually Latin, as in ment).
When -chen is a suffix to a root word, then the word with said suffix will be neuter.
Example: Der Baum but das Bäumchen.
However, not all occurrances of these letters at the end of a word are a suffix. For example, the word der Rachen is not composed of a root *Ra- plus suffix *-chen; it actually is an entire (masculine) root by itself Rachen. It would be possible to add the -chen suffix to Rachen creating das Rachenchen (but that doesn’t make a whole lot of semantic sense).
In the case of -um, this is a suffix on Latin words all of which (to the best of my knowledge) have been imported into German as neuter words. However, there are entirely unrelated non-Latin words that just happen to end with these letters without being influenced by the Latin origin.
* I contest the validity of some of those entries like -til or -ma. I don’t believe they are suffixes nor that they can be reasonably used to guess a word’s grammatical gender.
