Repetition is the simple repeating of a word, within a sentence or a poetical line, with no particular placement of the words, in order to provide emphasis. This is such a common literary device that it is almost never even noted as a figure of speech. It also has connotations to listing for effect and is used commonly by famous poets such as Philip Larkin.
Today, as never before, the fates of men are so intimately linked
to one another that a disaster for one is a disaster for everybody. (Natalia Ginzburg, The Little Virtues, 1962)
Antanaclasis is the repetition of a word or phrase to effect a different meaning
"We must all hang together, or assuredly we shall all hang separately." (Benjamin Franklin)
Epizeuxis or palilogia is the repetition of a single word, with no other words in between. This is from the Greek words, "Fastening Together"
Conduplicatio is the repetition of a word in various places throughout a paragraph.
"And the world said, 'Disarm, disclose, or face serious consequences'—and therefore, we worked with the world, we worked to make sure that Saddam Hussein heard the message of the world." (George W. Bush)
Anadiplosis is the repetition of the last word of a preceding clause. The word is used at the end of a sentence and then used again at the beginning of the next sentence.
"This, it seemed to him, was the end, the end of a world as he had known it..." (James Oliver Curwood)
Anaphora is the repetition of a word or phrase at the beginning of every clause. It comes from the Greek phrase, "Carrying up or Back".
"We shall fight on the beaches, we shall fight on the landing grounds, we shall fight in the fields and in the streets, we shall fight in the hills, we shall never surrender." (Winston Churchill)
Epistrophe is the repetition of a word or phrase at the end of every clause.
"What lies behind us and what lies before us are tiny compared to what lies within us." (Ralph Waldo Emerson)
Mesodiplosis is the repetition of a word or phrase at the middle of every clause.
"We are troubled on every side, yet not distressed; we are perplexed, but not in despair; persecuted, but not forsaken; cast down, but not destroyed..." (Second Epistle to the Corinthians)
Diaphora is the repetition of a name, first to signify the person or persons it describes, then to signify its meaning.