Embryonic
Part of speech: adjective
Definition: Of or related to an embryo. Something, especially a project, that is very new and is still evolving; something that has yet to reach its full potential.
Immature
Part of speech: adjective
Definition: Not fully formed or developed, unripe.Childish in behavior.
Example sentence: I don't pay attention to the number of birthdays. It's weird when I say I'm 53. It just is crazy that I'm 53. I think I'm very immature. I feel like a kid. That's why my back goes out all the time, because I completely forget I can't do certain things anymore - like doing the plank for 10 minutes.