This is the 11105th most frequent Spanish word.
electrónicas
"Electrónicas" means "electronic" or "electronics" in English, depending on context.
In this sentence, 'electrónicas' is used as an adjective describing 'guitars,' implying guitars that use electronic components.
Las guitarras electrónicas suelen tener muchas funciones adicionales.
Electronic guitars often have many additional features.
Here, 'electrónicas' functions as an adjective for 'encyclopedias,' suggesting that the encyclopedias are in digital, electronic format.
Las enciclopedias electrónicas son una fuente útil de información.
Electronic encyclopedias are a useful source of information.
In this case, 'electrónicas' modifies 'estructuras,' indicating structures related to or involving electronics.