荷物 and 持ち物: baggage and belongings
Distinguish baggage to carry or store from belongings or items someone should bring.
Baggage to carry or leave
荷物 is read にもつ and refers to baggage carried on a journey or goods being transported. 「駅で荷物を預けました」 means that the speaker left their baggage at the station.
「荷物が届きました」 says that baggage or a package has arrived. 荷物 is not restricted to a single travel suitcase.
Belongings or items to bring
持ち物 is read もちもの and refers to personal belongings or required items. 「持ち物に名前を書いてください」 asks people to write their names on their belongings.
In event instructions, 「持ち物：水、タオル」 lists water and a towel as things to bring. The list does not state that participants already have those items with them.
Different perspectives on the same objects
A suitcase can be 荷物 to transport, while the personal items inside can be 持ち物. Focus on transportation versus personal possession or preparation rather than size alone.
「荷物を軽くするため、持ち物を減らしました」 means that the speaker reduced the items they would bring to lighten the baggage. Reducing the items is completed; lightening the baggage is its purpose.
Which word fits the heading for items to bring on an outing?
Show the answer and why
持ち物 fits. 「持ち物を確認してください」 asks people to check what they need to bring, not to ship or store their baggage.