Expressing “to make a speech” with 发言 and 发表
The verbs 发言 and 发表 are similar in their translation, but we should use them in different contexts.
The verb 发表
We use the verb 发表 
to emphasize that a person or group of people are making an official statement.
to emphasize that a person or group of people are making an official statement.Examples
政府发表声明谴责这些凶杀事件
The government released a statement condemning the killings
zhèngfǔ fābiǎo shēngmíng qiǎnzé zhèxiē xiōngshā shìjiàn
他们发表联合声明否认指控
They released a joint statement denying the allegations
tāmen fābiǎo liánhé shēngmíng fǒurèn zhǐkòng
We also use the verb 发表 in the meaning of “to publish” when talking about publishing articles.
Examples
我的文章以节录的形式发表了
My article was published as an excerpt
wǒ de wénzhāng yǐ jiélù de xíngshì fābiǎo le
发表该文章的杂志将受到诽谤诉讼
The magazine that published this article will be prosecuted for slander
fābiǎo gāi wénzhāng de zázhì jiāng shòudào fěibàng sùsòng
The verb 发言
We use the verb 发言 when talking about a person speaking at a meeting or in a classroom.
when talking about a person speaking at a meeting or in a classroom.Examples
老师希望你多发言，说出你自己的想法，意见
The teacher hopes that you will speak more and express your own ideas and opinions
lǎoshī xīwàng nǐ duō fāyán, shuōchū nǐ zìjǐ de xiǎngfǎ, yìjiàn
教授获邀就自己的研究成果发言
The professor was invited to speak about his research
jiàoshòu huò yāo jiù zìjǐ de yánjiū chéngguǒ fāyán
她被指派代表我们发言
She was assigned to speak on our behalf
tā bèi zhǐpài dàibiǎo wǒmen fāyán
As a noun
We also can use 发言 as a noun for “performance", 'speech”.
Pay attention
We can not use 发表 as a noun.
Examples
他今天在会上的发言很精彩
He gave a great speech at the conference today
tā jīntiān zài huì shàng de fāyán hěn jīngcǎi
总统的大会发言受到了好评
The President's convention speech was well received
zǒngtǒng de dàhuì fāyán shòudào le hǎopíng