【Introduce】 ,  【insert】 ,  【insinuate】 ,  【interpolate】 ,  【intercalate】 ,  【interpose】 ,  【interject】  mean to put something or someone in a place among or between other things or persons.

【Introduce】  (see also ENTER 2 ) implies a bringing forward of someone or something not already in company with the other persons or things, but it also suggests as the aim of such an act the placing of the person or thing in the midst of that group or collection so as to form a part of it.

【Insert】  implies a setting of a thing in a fixed place between or among other things; thus, to  【insert】  lace in a garment is to put it between two pieces of the material which forms the garment; to  【insert】 leaves in a book is to put leaves into their proper places (as by the use of glue).

【Insinuate】  (see also SUGGEST ) implies a slow, careful, often gentle or artful introduction (as into or through a narrow or winding passage) by pushing or worming its or one's way.

【Interpolate】 implies the insertion of something that does not belong to and requires to be distinguished from the original, whether because it is extraneous to the subject under discussion or because it is spurious or simply because it is in fact not part of the original.

【Intercalate】 primarily implies an insertion in the calendar (as of a day or month), but in its extended sense it implies insertion into a sequence or series, then often also connoting intrusion.

【Interpose】  (see also  【INTERPOSE】 2 ) differs from  【interpolate】 mainly in its implication that what is inserted serves as an obstacle, obstruction, or cause of delay or postponement.

Of all of these words,  【interject】 carries the strongest implication of abrupt or forced introduction. The word is often employed in place of said in introducing a remark, statement, or question that comes more or less as an interruption or addition.