Answer:
literary allusion
Step-by-step explanation:
A literary allusion occurs when a literary work makes an explicit reference to another literary work, to a character or a quote from another literary work. In addition, reference to real people can also be made according to the concept of literary allusion.
Based on this, we can say that the title of Things Fall Apart by Achebe is an example of literary allusion because it represents a direct reference to the third and fourth line of the poem "The Second Coming" by Yeast. The referenced lines are:
"Things fall apart; the centre cannot hold;
Mere anarchy is loosed upon the world"