occur
Occorrere is an Italian verb that means 'to occur' or 'to happen'. It is a verb that is often used in the infinitive form and is usually followed by the preposition 'di' to indicate what is happening or occurring. For example, 'Occorre di fare attenzione' means 'It is necessary to be careful'.
You don't need to worry.
This sentence uses 'occorrere' in a negative command form, telling someone that it's not necessary for them to worry.
You need to have lunch before leaving.
In this context, 'occorrere' is interpreted as 'being necessary', implying that it's a requirement to have lunch before going on a journey.
It takes rain to grow plants.
This sentence expresses that rain is a necessity or requirement for the growth of plants, hence it 'takes' or it's 'needed', which is the meaning of 'occorrere'.