Apology, n.; pl. Apologies .
Etymology: [L. apologia, Gr. apologie. See Apologetic.]
1. Something said or written in defense or justification of what appears to others wrong, or of what may be liable to disapprobation; justification; as, Tertullian's Apology for Christianity. It is not my intention to make an apology for my poem; some will think it needs no excuse, and others will receive none. Dryden.
2. An acknowledgment intended as an atonement for some improper or injurious remark or act; an admission to another of a wrong or discourtesy done him, accompanied by an expression of regret.
3. Anything provided as a substitute; a makeshift. He goes to work devising apologies for window curtains. Dickens.
Syn. -- Excuse. An apology, in the original sense of the word, was a pleading off from some charge or imputation, by explaining and defending one's principles or conduct. It therefore amounted to a vindication. One who offers an apology, admits himself to have been, at least apparently, in the wrong, but brings forward some palliating circumstance, or tenders a frank acknowledgment, by way of reparation. We make an apology for some breach of propriety or decorum (like rude expressions, unbecoming conduct, etc.), or some deficiency in what might be reasonably expected. We offer an excuse when we have been guilty of some breach or neglect of duty; and we do it by way of extenuating our fault, and with a view to be forgiven. When an excuse has been accepted, an apology may still, in some cases, be necessary or appropriate. "An excuse is not grounded on the claim of innocence, but is rather an appeal for favor resting on some collateral circumstance. An apology mostly respects the conduct of individuals toward each other as equals; it is a voluntary act produced by feelings of decorum, or a desire for the good opinion of others." Crabb.
1 other Webster entry under this spelling
Apology, v. i.
To offer an apology. [Obs.] For which he can not well apology. J. Webster.
Shades of meaning
All these words express one's answer to a charge of wrong or error that is or might be made. Apology has undergone a remarkable change from its old sense of a valiant defense--as in Justin Martyr's Apologies for the Christian faith--to its present meaning of humble confession and concession. He who offers an apology admits himself, at least technically and seemingly, in the wrong. An apology is for what one has done or left undone; an excuse may be for what one proposes to do or leave undone as well; as, one sends beforehand his excuse for not accepting an invitation; if he should fail either to be present or to excuse himself, an apology would be in order. An excuse for a fault is an attempt at partial justification; as, one alleges haste as an excuse for carelessness. Confession is a full acknowledgment of wrong, generally of a grave wrong, with or without apology or excuse. Plea ranges in sense from a prayer for favor or pardon to an attempt at full vindication. Defense, exculpation, justification, and vindication are more properly antonyms than synonyms of apology in its modern sense, and should be so given, but for their connection with its historic usage. Compare confess; defense.
Prepositions
An apology to the guest for the oversight would be fitting.