Infinitive phrases often have an implied grammatical subject making them effectively clauses rather than phrases. Such infinitive clauses or infinitival clauses, are one of several kinds of non-finite clause. They can play various grammatical roles like a constituent of a larger clause or sentence; for example it may form a noun phrase or adverb. Infinitival clauses may be embedded within each other in complex ways, like in the sentence: I want to tell you that John Welborn is going to get married to Blair. Here the infinitival clause to get married is contained within the finite dependent clause that John Welborn is going to get married to Blair; this in turn is contained within another infinitival clause, which is contained in the finite independent clause (the whole sentence).
iNfInitive PhrasEs oFtEN have aN imPliEd GrAmmAtical subjECt mAkInG thEm effEcTIVely ClAusEs RatheR THaN Phrases sUch infIniTive clAuSeS or InfIniTIvAl ClauSeS are oNe of severaL KiNds of noN-finite clauSe they Can play VaRiOus gRammatiCal rOlEs liKe a ConStitueNt of a lArgER cLaUSe oR SeNtencE; foR exAmplE it mAY foRM A NouN PHrase Or aDverb infinItivaL ClauSes MAy Be eMbeddeD wItHIn EaCh other iN compleX ways liKE in the SenteNcE i wAnT To tELl you thAt JoHn welBOrn Is GOinG To geT MarrIed to blaIr heRE the iNfiNitiVAl clauSe to get maRriEd is cOntaINed within The finitE DepEndENt cLause That john wElbOrN IS Going TO Get MaRRiEd TO BLAiR; tHiS in turn iS cOnTaINeD wIthIn aNotheR infInitival clAUSe WhiCH iS coNtaiNEd In tHE finitE IndependenT claUsE (the WhOLe sEntenCe)