Many elements that constitute a language are actually special features rather than linguistic requirements, so I've decided to go through the features I've come across so far. If someone knows any other special features, tell me and I'll add them.
Among the most "Natural" features for many western IE speakers are the definite of a noun. It is a feature that indicate the item in question is either already mentioned or you both have a pre-existing knowledge of what specific one you are refering to. But most languages dont have it and just refers to "the car" and "a car" simply as "a car" in all instances. It isnt needed nor common outside of western european languages (even non-IE)
Plural is also a common feature for many languages but not all have it, especially creols are known for lacking it and you simply say "one bullet" and "many bullet".
Dual is simply two fo something, if it does exist it already has plural and is more marked than Plural, PIE had it, few still do.
Very rare but have been documented, dual and plural must exist already for this one.
Well documented and is simply a few, must have plural for this one
Gender is extremely common in languages for reasons not quite known but it is a mere subdivision of nouns into a set of groups which may, or may not, effect the declension of the noun in question. English lack this
A manner which it is shown on the noun their intended purpose in the sentence. Not neccisery as croels often lacks it and adositions and more can fullfill most case purposes
Tenses are not neccisery for a language and many languages have only aspects that refers to wether an action is ongoing or completed for present and past but they are not tenses in the aspect we know it.
Alot of them exist but non is necciery really and one could soley rely on tenses
More to come and fillout to be done