What is the irony in the title "Marriage Is a Private Affair"?

The title is also ironic because it uses the word "affair," which can mean several different things. 

The word "affair" can refer to an incident or an occurrence. As the other educators pointed out, it can also refer to a private matter or concern. However, another meaning of the word is understood as, "an illicit relationship or dalliance."

The title states that "marriage is a private affair." Normally, no one would refer to a marriage as an illicit dalliance. In fact, marriage is a public declaration of fidelity. As is the usual practice, "forbidden" affairs are often conducted in secret, and the parties involved are usually not too keen on their secret being discovered. Much is at stake in such an arrangement.

In Achebe's story, the title indicates what is made clear in the story. The groom's father (Okeke) makes his disgust with his son Nnaemeka's impending marriage to Nene public knowledge in his community. The men from Okeke's community unequivocally sympathize with Okeke's grief and anger. They condemn in blistering terms Nnaemeka's rebellious insistence on marrying Nene. In fact, the men characterize Nnaemeka's actions as a grave sin against his parent and God.

In characterizing Nnaemeka's actions in this manner, both Okeke and his male compatriots have reduced holy matrimony between two people to the level of an immoral dalliance. In these men's eyes, Nnaemeka and Nene's marriage is not a sacred, lasting alliance but a wicked sexual flirtation that is bound to fail. In Nnaemeka and Nene's case, the irony in the title is clear: far from their marriage being a sacred alliance, it is now a "private affair," something to be ashamed of within the confines of Ibo culture. 

What is the irony in the title "Marriage Is a Private Affair"?

Chinua Achebe's short story "Marriage is a Private Affair" is about the cultural and generational problems which arise when a man from the Ibo tribe wants to marry a girl from the Ibibio tribe of Nigeria. Nnaemeka is hesitant to tell his father about his impending marriage to Nene, because he believes his father will be against him marrying outside his own ethnic group. He is right and his father basically disowns him. 

The title is an example of verbal irony where language is used to say one thing but means the opposite. It is quite ironic because the marriage is far from "private." It is thoroughly discussed among the men in Nnaemeka's father's village. It is, in fact, quite an important topic in the village as it was rare for someone to marry out of their group. The men of the village are shocked and lament that a son has risen against his father. The marriage is also a topic of discussion among the Ibo women in the relatively cosmopolitan city of Lagos, where the couple lives. They initially disapprove but eventually overcome their prejudice and accept Nene into their group. The father too is on the verge of acceptance at the end of the story.

Justify the title "Marriage is a Private Affair."

I think that the title of Achebe's work is justified in the character of Okeke.  Through his own evolution and change, the father ends up learning that marriage is, indeed, a private affair.  Okeke is quite insistent that marriage be seen as a public matter.  In the opening of the narrative, marriage is viewed as a public affair in how he selects a bride for his son and the insistence with which he pursues his son's marriage.  While he shuns his son in a callous and cold manner, he remains convinced that marriage is a public affair.

All this changes in the resolution of the story.  The letter from Nene shows that the marriage between Nnaemeka and Nene has been successful, and with children.  These children wish to meet their grandfather.  Nene's letter proves that the title is justified as she asks Okeke to meet his son and grandchildren.  For her part, she will remain in Lagos.  Such an action validates the private condition of marriage.  It is something that she will not sacrifice for her father- in- law.  Her asking him to meet his grandsons without her presence helps to justify how her marriage is and will always be a private affair.  Okeke realizes this when he contemplates his actions in shutting out his grandchildren, awaking with a fear that he might never have a chance to right his wrong.  This realization demonstrates how he has come to understand that marriage is a private affair, something that he has to concede if he wishes to see his grandchildren.  In this, the title of the work is justified as the characters have come to embrace its truth and validity.

What is the significance of the title in Achebe's "Marriage is a Private Affair"?

I think that Achebe's title helps to assess what one thinks of the marriage between two people.  Consider that Okeke is characterized that thinking that marriage is not a private affair.  He refuses to acknowledge the private and sanctified feelings that his son feels.  He repudiates any notion that marriage is private and something that exists between his son and Nene.  Okeke is someone who would reject the title from an initial point of view.  Yet, as the story progresses, this view of marriage is not something that is continued to be accepted.  Especially so in the ending when Okeke feels a sense of dread and foreboding about how he had carried himself, he comes to understand the private nature of not merely marriages, but feelings, in general.  The emotions he experiences about the abandonment of his son and grandsons is something that he feels in a private way, a sort of negative analog of the feelings that his son felt.  Whereas the son felt joy and happiness and his marriage, Okeke realizes his own private feelings of guilt and regret at the end.  In this, not merely marriage, but all emotions, are seen as privatized entities.  It is here where the title gains significance in the face of Okeke's transformation.