For plural we always use the S. 
 
Castillian (so called Spanish): 
 
Un (cuchillo) Corvo, dos Corvos. 
Un (pajaro) Cuervo, dos Cuervos. 
 
Portuguese: 
 
Um (passaro) Corvo, dois Corvos. 
 
Spanish Galician:(*) 
 
Un (paxaro) corvo, dous corvos. 
 
(*) 
Galician (Galego) is often similar or equal to Portuguese.
		 
		
		
		
		
		
		
		
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