but the becomes bə ðə. what name is this process ?

[semantics12345]

What do we call sounds like these ?

But the ----- bə ðə

But by ------ bə baɪ

that my ----- ðə maɪ

Do these example represent deletion process of the sound [t]?

[raindoctor]

1. lagging assimilation, along with tapping.
2/3. stop 1 + stop 2 > stop 2 ( a known phenomenon in lower register)