This is the 250th most frequent Polish word.
sieci
The Polish word "sieci" means "nets" or "networks" in English.
Here, 'sieci' is the plural form of 'network' or 'net', referring to physical fishing equipment.
Ryby złapały się w sieci rybackie.
The fish got caught in the fishing nets.
In this context, 'sieci' refers to business chains, such as chains of stores or cafes.
Obie sieci kawiarni mają specjalne oferty na wiosnę.
Both café chains have special offers for spring.
Here, 'sieć' (singular, but implying 'sieci' in general) refers to a connected system of computers, i.e., a computer network.