When 一 下 yíxià is preceded by a verb, it has the following two functions.

 1. It is used as a time measure to imply that an action lasts for a short time

1）wǒ yònɡ yí xià hǎo mɑ ？
    我 用   一 下  好  吗 ？
    Could I use it for a little while?

2） wǒ chūqù yíxià.
     我出去一下。
     I go out for a little while.

2. Verb 一 下 yíxià is used to soften the tone of voice, as leaving a verb at the end of a sentence sounds too definite, or even rather crude.
There are two other formulas that have the same function.

1). Reduplication of verbs, as in

wǒ ɡěi nǐ jiè shào jiè shào 。 。 。 。 。 。
我 给  你 介  绍   介  绍   。 。 。 。 。 。
Let me introduce you...

wǒ xiān xiǎnɡ xiǎnɡ 。
我 先   想    想    。
Let me think (about it) first.

2). The verb 一 yi verb pattern, as i

qǐnɡ shuō yī shuō 。
请   说   一 说   。
Please talk about it.

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