Age

What typically one means with age, is, the amount of time passed from the exiting of the newborn from the carriers body.
Easy, right? No, the matter is much more complex. But before we continue to explain that, we need to introduce a few concepts:
first of all we need to differentiate between two things: body age and mental age.

Body Age

First lets start with body age. Reason being that it is the simpler of the two.
Body age is the age of the vessel of an entity, so, the typically referred age as described above.
For example if entity Freya was born 25 years ago, Freya's body age is 25 years.

Mental Age

Lets first make a small experiment.
Take an entity who u do not know their age and their physical appearance. So, for example an online friend. Then, keep attention to one thing: while talking and chatting to eachother (keep in mind that if the voice is unknown this experiment works better, but isnt necessary) try to keep track of one thing: based on their way to do the conversation, try to guess what their age is, an approximation is enough. Then ask the entity in question their body age and compare the two: u will notice that, these often are not the same. might be off by a few years but it could also be decades!
If u manage to guess the age right, continue to redo the experiment until u find a missmatch, eventually one will be found.
What is mental age then?

Mental age is the age that the entity shows to posses.
A good example of this are age regressors, who many times also know what their mental age is themselves, and many times that can missmatch to the body age even 10 years or more!

Age and Consent

In the current society, the ability to give consent is legally defined by their body age. But, u will probably notice there is something not quite right: why is it the body age and not the mantal age?
Yes, practically it is because determinating the mental age and ability to consent for every single entity wouldnt be doable. A kid that is developing faster mentally might be able to give informed consent before a kid that takes a bit longer. One might then conclude, mental age is the threshold for consent.
Wrong, don't fall in this trap.

I will simply proove it by an example. Take an age regressor with body age 21 and mental age, as defined by themselves 7. Thing is, while mentally they are 7 they still passed 21 years of their life. They aquired knowledge, and are so perfectly able to give informed consent. They are not stupid, they simply behave in a way an average entity of body age 7.
So what do we learn from here? Age and ability to consent are 2 separate things.
Note tho, that generally speaking, the ones with younger physical age have difficulties to give informed consent, but that is related with the aquiring of knowledge, that, inevitably takes its time.
To have informed consent u have to be sure that the entity is able to understand the topic and implications of one choice and another. Age on its own doesn't play a role.

What is Age then?

Age is a social construct. Age is much more complex than it seems, and society gives it too much importance in the wrong way, for example in consent. Age doesn't really matter, and is a made up thing for convenience, that is tho misleading and false.
U might have noticed something: the concept is similar if not the same as gender, that also is a social construct.