verb
1
BAD : The concert will occur at eight o'clock next Tuesday.
GOOD : The concert will take place at eight o'clock next Tuesday.
◆◆◆
Occur is usually used in connection with unplanned events: 'Many of the serious accidents that occur are caused by human error.' 'Tornadoes occur when a warm weather front meets a body of very cold air.'
For planned events, use take place : 'The wedding will take place at St Andrew's church.'
2
BAD : You'd better tell them exactly what occurred.
GOOD : You'd better tell them exactly what happened.
◆◆◆
Occur is used mainly in formal styles: 'These violent incidents frequently occur without any warning.'
The usual word is happen : 'The accident happened just outside my house.'