What’s the difference between 二五 and 二十五?

Question

Can I just say 二五 when I’m talking or counting instead of 二十五? Will it make a difference between the two of them? Or is it because 二五 is like everyday speech (informal) and 二十五 (formal) for writing?

I watched 奔跑吧第 “Keep Running” show in order to learn and improve my chinese. I remembered in one of the episode of the show, the members were counting without 十 between numbers. I’m trying to learn the “everyday” chinese by watching chinese dramas and variety shows in order to improve my comprehension and speech.

Answer 1

the members were counting without 十 between numbers.

This is exactly where the "十" can be completely omitted, when one is counting. It is quite normal to omit the "十" after passing 20 when counting, especially when one is counting fast.

I cannot recall other circumstances when the "十" can be omitted.

Also, one might drop the hundred part completely after 100, starting from 一 again. The hundred part is may be only included when a whole hundred is reached. E.g. 九七, 九八, 九九, 一百, 一, 二, 三, 四, ......, 九七, 九八, 九九, 二百, 一, 二, 三, 四, ...... The hundred part is memorized instead of spoken out. (Sometimes one might use fingers to keep track of the number of hundreds)

Disclaimer: I am a native Chinese speaker in Beijing. This may differ in different regions or in different dialects.

Answer 2

When it is an amount, 二十五 cannot be reduced to 二五

In the clip, the man was counting 25, 26... . He was reading out the digits on a stopwatch (not an amount)

If you hear someone counting "一五，二五，三五，四五", that person is citing the 乘數表 (multiplication table). Counting a group of five items as a time,

Column 5 in multiplication table:

一五得五 (1 X 5 = 5)

二五得一十 (2 X 5 = 10)

三五一十五 (3 X 5 = 15)

四五中二十 (4 X 5 = 20)

五五二十五 (5 X 5 = 25)

六五中三十 (6 X 5 = 30)

七五三十五 (7 X 5 = 35)

八五中四十 (8 X 5 = 40)

九五四十五 (9 X 5 = 45)

Side note: 二五 could be short for 二五仔 which is Cantonese slang for traitor

Answer 3

Using 二五 ("two five") in place of 二十五 ("twenty five") would be considered incorrect (so don't use it on a Chinese test). However, in the video it's possible the pronunciation of 十 is partly (if not wholly) swallowed if the people are speaking quickly and repetitively, or are speaking with a dialect.

This succinct pronunciation is common for native Chinese speakers, and there are many typical examples of it presented in the YouTube video Understand FAST Chinese Conversations | Common Reductions in Everyday Speech.

I expect the 十 in 二十五 sounds like a brief grunt between 二 and 五, like when people pronounce 不知道 (bù zhī dào) as "bù r dào" or even just "bù ào".