Simplify the following text for a Grade 4 native English-speaking person.
Original: The javelin throw is a track and field athletics throwing event where the object to be thrown is the javelin , a spear approximately 2.5 metres in length . Javelin is an event of both the men 's decathlon and the women 's heptathlon .
Simplified: The javelin throw is a sport event , a part of the track and field .