How do you know something is a delusion?

I was walking down the hall to L’s room. I knocked on her door to see if she was there. I happened to glance further down the hall when she didn’t answer and saw a white girl with dark brown hair in a pony tail, work out shorts, and loose t-shirt. I figured she either was probably going to work out or had just worked out. I decided to follow her and ask if she wanted to work out with K (another friend of mine) and I. I looked around the hall so I wasn’t staring straight at her (somehow I’ve noticed people can feel that and it creeps them out) but I was glancing at her at about 5 second intervals to make sure she didn’t go in a room, though I was pretty sure she was headed to the laundry room and I was going to ask her in there (I think subconsciously I wanted to check to see if there was a free washer too). I followed her for about 300 feet and she turned the corner to the much shorter hall where the laundry is. I heard her keys jingling intermittently. This whole time.
I turned the corner and she wasn’t there. That hall is about 20 feet long if that and dead ends. There is only one door and the laundry room on the other side.
I figured she was already in the laundry room (which is reasonable I was about 20 feet behind her, or more). When I looked in, no one was there. I didn’t hear her knock on the other door and the locks in my building are pretty loud so I would have heard it. Also K said the girls who live there are both black and this girl was obviously white so she probably wouldn’t have a key. She just disappeared.
I am pretty sure this was a hallucination, but I don’t feel creeped out. I feel like it was all normal. Does that make it a delusion?
My main question, though, is what is the difference between when normies hear things that aren’t there or see things that aren’t there (my Mom and others have said they sometimes hear people call their name when no one is there. Some times they see things differently like oh that’s Ellen. I thought that way June.) but diagnostically, what is the difference. When does it become a hallucination?

Hallucinations have to be ongoing for over six months and be interfering with normal life…like making you do things or not do things normally. A delusion is a false belief that someone believes in contrary to what is going on in reality (what others (normal people) perceive)

A constant hallucination such as seeing the same girl or can they be varied? Like seeing a girl one time a boy another and then a rabbit and that going on for over six months but with different people or things that you have come to find out aren’t there?

anything that other people dont see or that disappears. Doesnt have to be the same things. For example, you could see a mummy in your kitchen on monday and then see a rabbit running into a room the next day. Both are obviously hallucinations unless you have a pet rabbit or are throwing a halloween party…see what I mean?

Yeah. Thank you! I have always kinda wondered this.

Hallucination is a mental perceptions {or mental responses }with a stimulus
that does not exist in the external environment,like you see some people
that are not there,and hear voices of these people where no one can hear

if you think that these people are actual human beings,this is false belief
if you think that you hear the voice of god,this is false belife
if you belief in the meaning and content of the audible voices of these
people,this is false belief

2-the credibility of information about the hallucination
a-in the actual world,the doctor in his clinic can not listen to the voices with
his sense hearing “ear”
b-he can not listen to the voices via scientific audio devices
c-he could not diagnose the voices by self means or by scientific
d-in this situation,the doctor becomes a witness had not seen anything
the only witness is the schizophrenic individual,he is the source of real information
so that,if the doctor say that,the voices of hallucination is temporary not a fixed
and it is occurs for one day/week/ month/ year /years/ long term/ forever

whatever he say,his statement are not scientific facts,because it did not arise from
self observations or even a scientific experience

the sz regard with the doctor is just a diagnosing of symptoms,{ sensual observations}
but the sz regard with the schizophrenic is the audible voices {internal perceptions}

the main suffering for the individual with sz is the hearing of the voices
and the final recovery form the sz depend on the disappearing of the voices

that is to say,if you talking about a case of schizophrenia that have not the
phenomenon of hearing the voices,you are talking about different case,because
the sz in itself is the audible voices not any other symptoms or disorder

so that,if there is an individual have sz ,and he do not hearing the voices
all time of waking all days of years,he have final recovery from the schizophrenia

Hallucinations do not have to be constant. Some are short lived - one day yes, next day none for example. Delusions are beliefs that is not based in reality or true.

I think the only difference is if you talk about it or not.
Normal people experience odd stuff too, they just aren’t going to risk getting called mentally ill by talking freely about it.

Sometimes I have no idea I’m in the deeps of a delusion. It’s a belief and I believe it. I have a few that I recognize as things that have come up before and they we’re proved wrong then, and they are wrong now. But there are some that I’m still working through. There are some beliefs that hit into my head that I have to work around because I still believe the delusion.

that’s just it. u don’t, or it wouldn’t b a delusion. i have voices that lead my delusions but i can’t call them such anymore because i no longer believe what they say. if u r fully immersed and can’t tell if ur reality is the correct version then that is a delusion. ie: no insight. but if u can then it’s not a delusion. i no longer have delusions. voices tell me stuff. i say bollocks and that’s about it.