The difference between 语言 and 言语
Both nouns mean “language”, but these nouns are used differently.
The noun 言语
言语 
is used to talk about spoken language.
This noun has two main meanings:
1) "language", "speech".
is used to talk about spoken language.
This noun has two main meanings:
1) "language", "speech".Examples
醉酒影响言语能力和协调性
Intoxication affects speech and coordination
zuìjiǔ yǐngxiǎng yányǔ nénglì hé xiétiáo xìng
随着言语的发展，孩子开始把更多的词语连串起来
As the child’s speech develops, he begins to put more words together
suízhe yányǔ de fǎ zhǎn, háizi kāishǐ bǎ gèng duō de cíyǔ lián chuàn qǐlái
Pay attention
言语 is used rarely and only in colloquial speech.
2) "words".
Examples
言语无法表达我的愉快心情
Words cannot describe my happiness
yányǔ wúfǎ biǎodá wǒ de yúkuài xīnqíng
你能用很简单的言语把这再说一遍吗？
Can you say that again using simple terms?
nǐ néng yòng hěn jiǎndān de yányǔ bǎ zhè zài shuō yí biàn ma
The noun 语言
语言 is used to talk about the general concept of language.
It is used to form such expressions: “to learn the language”, “a language school”, “language grammar”. 言语 cannot be used in these expressions.
is used to talk about the general concept of language.
It is used to form such expressions: “to learn the language”, “a language school”, “language grammar”. 言语 cannot be used in these expressions.Examples
我慢慢开始学这个语言
I slowly began to learn this language
wǒ mànman kāishǐ xué zhè ge yǔyán
汉语是词形变化不丰富的语言
Chinese is not a language with various morphological changes
hànyǔ shì cí xíng biànhuà bù fēngfù de yǔyán
我和他显然没有共同语言
We clearly have no common language
wǒ hé tā xiǎnrán méi yǒu gòngtóng yǔyán
When a word meaning “language” is said colloquial speech, 语言 and 言语 can be interchangeable.
Examples
刚到国外时，因为语言不通，所以感到不适应
When I first went abroad, I felt uncomfortable with an unfamiliar language
gāng dào guówài shí, yīnwèi yǔyán bù tōng, suǒyǐ gǎndào bú shìyìng
刚到国外时，因为言语不通，所以感到不适应
When I first went abroad, I felt uncomfortable with an unfamiliar language
gāng dào guówài shí, yīnwèi yányǔ bù tōng, suǒyǐ gǎndào bú shìyìng