Crackdown generally means to deal with a problem that has existed for some time. Suppress can mean a few things: (http://www.merriam-webster.com/dictionary/suppress) 1)to end or stop (something) by force 2)to keep (something) secret : to not allow people to know about or see (something) 3)to not allow yourself to feel, show, or be affected by (an emotion) Eg: "The government is cracking down on gun violence." => the government is dealing with the problem of gun violence "The government is suppressing freedom of speech." => the government is trying to stop freedom of speech

- Crackdown is a noun. It is a situation in which someone starts to deal with bad or illegal behaviour in a more severe way. e.g. The police are having a crackdown on cyclists without lights. - Crack down is a phrasal verb. e.g. The library is cracking down on people who lose their books. - Suppress is a verb. It means to end something by force. e.g. The Hungarian uprising in 1956 was suppressed by the Soviet Union. It also means to prevent something from being seen or expressed. e.g. She couldn't suppress her anger. - Suppression is a noun. e.g. brutal police suppression of the riots e.g. the suppression of free speech