Why does the P come before the Q in relative displacement vector notation?

[Ultrimo]

We have 3 points. O, P, Q.

OP = r_P
OQ = r_Q
but why is QP _Pr_Q rather than _Qr_P?

I'm just starting M4 and I really like to understand everything. This doesn't make any sense to me and I can't find out online. I'm sure there's a logical reason for it to be like that. Is it because you go along to r_Q and then along to P?

 

[Mark44]

We have 3 points. O, P, Q.

OP = r_P
OQ = r_Q
but why is QP _Pr_Q rather than _Qr_P?

Your notation doesn't make any sense to me.

QP = OP - OQ

If the coordinate form of OP is <p₁, p₂>, and the coordinate form of OQ is <q₁, q₂>, then QP = <p₁ - q₁, p₂ - q₂>.

I'm just starting M4 and I really like to understand everything. This doesn't make any sense to me and I can't find out online. I'm sure there's a logical reason for it to be like that. Is it because you go along to r_Q and then along to P?