Difficult and Rigourous

Difficult adjective - Requiring considerable physical or mental effort.

Rigourous and difficult are semantically related in harsh topic. In some cases you can use "Rigourous" instead an adjective "Difficult", when it comes to topics like ambitious, challenging.

Nearby Word: difficulty

Difficult and rigourous are semantically related in ambitious topic. Sometimes you can use "Difficult" instead an adjective "Rigourous", if it concerns topics such as challenging.