Strong's #1163: dei (pronounced die)
 3d person singular active present of 1210; also deon deh-on'; neuter active participle of the same; both used impersonally; it is (was, etc.) necessary (as binding):--behoved, be meet, must (needs), (be) need(-ful), ought, should.
Thayer's Greek Lexicon:
 ͂ 
 
  dei 
 
 1) it is necessary, there is need of, it behooves, is right and proper
 
 1a) necessity lying in the nature of the case
 1b) necessity brought on by circumstances or by the conduct of others toward us.
 1c) necessity in reference to what is required to attain some end
 1d) a necessity of law and command, of duty, equity
 1e) necessity established by the counsel and decree of God, especially by that purpose of his which relates to the salvation of men by the intervention of Christ and which is disclosed in the Old Testament prophecies
 
 1e1) concerning what Christ was destined finally to undergo, his sufferings, death, resurrection, ascension
 
  Part of Speech: verb
Relation: third person singular active present of G1210
  Citing in TDNT: 2:21, 140
 
Usage:
This word is used 106 times:
Matthew 16:21: "disciples, how that he  must go unto Jerusalem, and"
Matthew 17:10: "scribes that Elijah  must first come"
Matthew 18:33: " Shouldest not thou also have had compassion on thy fellow servant, even"
Matthew 23:23: "mercy, and faith: these  ought ye to have done, and not to leave"
Matthew 24:6: "troubled: for all  these things must come to pass, but the end"
Matthew 25:27: "Thou  oughtest therefore to have put my money to the exchangers,"
Matthew 26:35: "unto him, Though I  should die with thee, yet will I not"
Matthew 26:54: "be fulfilled, that thus  it must be?"
Mark 8:31: "the Son of man  must suffer many things, and be rejected"
Mark 9:11: "scribes that Elijah  must first come?"
Mark 13:7: "be ye not troubled: for  such things must needs be; but the end"
Mark 13:10: "And the gospel  must first be published among all"
Mark 13:14: "prophet, standing where  it ought not, (let him that readeth understand,) then"
Mark 14:31: "vehemently, If I  should die with thee, I will not deny thee in any wise."
Luke 2:49: "ye not that I  must be about my Father's business?"
Luke 4:43: "unto them, I  must preach the kingdom of God"
Luke 9:22: "The Son of man  must suffer many things, and be rejected"
Luke 11:42: "love of God: these  ought ye to have done, and not to leave the other undone."
Luke 12:12: "same hour what  ye ought to say."
Luke 13:14: "days in which  men ought to work: in them therefore"
Luke 13:16: "And  ought not this woman, being a daughter of Abraham, whom"
Luke 13:33: "Nevertheless I  must walk today, and tomorrow, and"
Luke 15:32: "It  was meet that we should make merry, and be glad: for this thy"
Luke 17:25: "But first  must he suffer many things, and be rejected"
Luke 18:1: "a parable unto them  to this end, that men ought always to pray, and not"
Luke 19:5: "for today I  must abide at thy house."
Luke 21:9: "terrified: for these things  must first come to pass; but the"
Luke 22:7: "when the passover  must be killed."
Luke 22:37: "that this that is written  must yet be accomplished in me,"
Luke 24:7: "the Son of man  must be delivered into the hands of sinful"
Luke 24:26: " Ought not Christ to have suffered these things, and to enter into"
Luke 24:44: "you, that all things  must be fulfilled, which were written in the"
Luke 24:46: "it is written, and thus  it behooved Christ to suffer, and to rise"
John 3:7: "I said unto thee, Ye  must be born again."
John 3:14: "the wilderness, even so  must the Son of man be lifted up:"
John 3:30: "He  must increase, but I must decrease."
John 4:4: "And he  must needs go through Samaria."
John 4:20: "the place where  men ought to worship."
John 4:24: "and they that worship him  must worship him in spirit and"
John 9:4: "I  must work the works of him that sent me, while"
John 10:16: "fold: them also I  must bring, and they shall hear my"
John 12:34: "thou, The Son of man  must be lifted up? who is"
John 20:9: "the Scripture, that he  must rise again from the dead."
Acts 1:16: "and brethren, this Scripture  must needs have been fulfilled, which the Holy"
Acts 1:21: "Wherefore  of these men which have companied with us all the time that"
Acts 3:21: "Whom the heaven  must receive until the times of restitution"
Acts 4:12: "among men, whereby we  must be saved."
Acts 5:29: "other apostles answered and said,  We ought to obey God rather than"
Acts 9:6: "the city, and it shall be told"
Acts 9:6: "the city, and it shall be told"