でいらっしゃる details
honorific "is" — the copula raised to the person it describes
失礼ですが、山田様でいらっしゃいますか。
shitsurei desu ga, yamadasama de irasshaimasu ka.
Excuse me — would you be Mr Yamada? formal
こちらが本校の校長でいらっしゃいます。
kochira ga honkou no kouchou de irasshaimasu.
This is our school's principal. formal
- noun
- na-adjective
- past
- polite
- polite negative
Examples
is; are — honouring the person the sentence is about, where です would leave them unmarked
失礼ですが、山田様でいらっしゃいますか。
shitsurei desu ga, yamadasama de irasshaimasu ka.
Excuse me — would you be Mr Yamada? formal
こちらが本校の校長でいらっしゃいます。
kochira ga honkou no kouchou de irasshaimasu.
This is our school's principal. formal
先生、その後もお元気でいらっしゃいますか。
sensei, sonogo mo o genki de irasshaimasu ka.
Professor, have you been keeping well since we last met? formal
Formation
{N}でいらっしゃるattaches to noun{NA-stem}でいらっしゃるattaches to na-adjective
Notes
(田中でございます), never ×田中でいらっしゃいます.
Related patterns
Similar
尊敬語 raises what a person DOES (いらっしゃいます, お読みになります); でいらっしゃいます raises what they ARE, which is the one thing a verb-based honorific cannot reach — 社長です has no honorific until the copula itself is replaced.
Two halves of the same job — お〜になる honours a verb, でいらっしゃる the copula; a sentence introducing someone therefore needs でいらっしゃる however many お〜になる it already contains.
Lookalikes
Same いらっしゃる, two hosts a kana apart — 住んでいらっしゃいます is the て-form plus いらっしゃる and honours an ongoing action, while 会長でいらっしゃいます is the copula itself and honours who the person is.
The classic mix-up at a reception desk — でございます merely polishes the copula and is the form you use about yourself and about things (田中でございます), while でいらっしゃいます raises the person it describes, so it must go to the guest (山田様でいらっしゃいますか) and never to yourself.