千

English lets 'thousand' stand alone, so learners try 千个. Chinese usually puts a number before 千 when you mean exactly one thousand. You can say 几千个 for 'several thousand' or 上千个 for 'over a thousand.' But for one thousand, the natural daily form is 一千个. Bare 千个 may appear in formal or literary phrases, but it sounds incomplete in normal chat.

Chinese counts big numbers in four-digit blocks, not English three-digit blocks. The units go 个, 十, 百, 千, then 万. Once you pass 千, you move to 万. So 100,000 is 十万, which means ten 万. You do not stack another 千 to say 一百千. This is why 1,000,000 is 一百万, not 一千千. “零百千万亿， 可以医椅衣。” (Zero, hundred, thousand, ten thousand, hundred million - they can sound like 'doctor,' 'chair,' 'clothes.') ── [《一二三（2）》](/read/counting-days-rhymes#s3)

Chinese often shortens hundreds after 千 in everyday speech, especially with money, rent, and prices. 一千五 means 一千五百, or 1,500. If you say 一千零五, that means 1,005 because 零 marks the empty hundreds place. So the short form only works when the hundreds digit is present. For formal writing or careful speech, say 一千五百.

When Chinese speakers say a year, they usually read each digit one by one. 1998 is 一九九八, then add 年. Saying 一千九百九十八年 sounds like you are reading a huge quantity, not a calendar year. The same pattern applies to phone numbers, room numbers, and many IDs. 千 is for amounts and measurements, not for calendar years.