1: μέλλω
(Strong's #3195 — Verb — mello — mel'-lo )

"to be about to" (for the significance of which see SHALL), e.g., Mark 10:32 , RV, "were to;" Luke 19:11 , RV, "was to;" "should" in Luke 22:23; 24:21; John 6:71; 7:39 , RV, "were to;" John 11:51; 12:4,33; 18:32; Acts 11:28; 23:27 , RV, "was about (to be slain);" 1—Thessalonians 3:4 , RV, "are to;" Revelation 6:11 . See ABOUT , B.

2: δεῖ
(Strong's #1163 — Verb — dei — die, deh-on' )

"it needs, it should," e.g., Matthew 18:33; Acts 27:21 : see MUST.

1—Corinthians 9:10