This is the 4069th most frequent Russian word.
нефтехимика
The Russian word "нефтехимика" means "petrochemist" in English, referring to a specialist in petrochemistry.
In this context, 'нефтехимика' ('petrochemist') is used in the accusative case as the direct object of the verb 'пригласили' ('invited').
Нефтехимика пригласили на конференцию, где он выступил с докладом.
The petrochemist was invited to the conference, where he delivered a report.
Here, 'нефтехимика' ('petrochemist') is in the genitive case indicating possession, referring to the experience belonging to the petrochemist.
Опыт нефтехимика помог в разработке нового топлива.
The petrochemist's experience helped in the development of new fuel.
In this example, 'нефтехимиком' ('petrochemist') is in the instrumental case showing the means or accompaniment by which the action was performed.