"第幾"

https://groups.google.com/d/topic/alt.usage.english/Ve_mmYlyHDM/discussion
[quote]
"Where do you come in your family?" (a bit vague but probably understandable)
"Where do you ....
"Where do you ...
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https://groups.google.com/d/topic/alt.usage.english/qdOnNxBlcaA/discussion

https://groups.google.com/d/topic/alt.usage.english/LnZVdAPGhN4/discussion
[quote]
This question is asked here about once a month.  There is no English
question word for the concept.
[end quote]

"Practical English Usage" by Michael Swan, 3e, page 228
252.5 ......
[quote]
Note that English does not have a special expression to ask for ordinal numbers (first, second etc).
It's our wedding anniversary. ~Congratulations. Which one? (NOT ... the how manyeth?
[end quote]