Ferrocarril (railway), Ferrocarriles
Madreselva (honeysuckle), Madreselvas
In the following compound nouns formed of an adjective and a noun, the adjective remains invariable in the plural, as—
Bajamar (low tide), Bajamares
Bajorelieve (bas-relief), Bajorelieves
Belladona (belladonna), Belladonas
Blancomanjar (blanc-mange), Blancomanjares
Plenamar (full tide), Plenamares
Salvoconducto (safe conduct), Salvoconductos
Salvaguardia (safeguard), Salvaguardias
Santa Bárbara (powder magazine), Santa Bárbaras
In compound nouns formed of two words, the first of which has suffered the loss or change of a letter, this first component remains invariable—
(N.B.—Many such words are found in Spanish.)
Artimaña (trick), Artimañas
Barbicano (white-bearded man), Barbicanos
Barbilindo (beardless man), Barbilindos
Boquirrubio (rosy-lipped), Boquirrubios
Cojitranco (lame fellow—disparagingly), Cojitrancos
Cuellierguido (stiff-necked man), Cuellierguidos
Gallipavo (turkey), Gallipavos
Manirroto (spendthrift), Manirrotos
Marisabidilla (blue stocking), Marisabidillas
Ojinegro (black-eyed), Ojinegros
Ojizarco (blue-eyed), Ojizarcos
Patizambo (bandy-legged), Patizambos
Pechicolorado (robin redbreast), Pechicolorados
Pleamar (high tide), Pleamares
Tragicomedia (tragi-comedy), Tragicomedias
Viandante (wayfarer), Viandantes
The following make their plural as follows—
Bancarrota (bankruptcy), Bancarrotas
Coliflor (cauliflower), Coliflores
Dares y tomares (wrangling), used only in pl.
Dimes y diretes (ifs, ands and buts), used only in pl.
Don Diego de noche (four o'clocks—flower), Don Diegos de noche
Maritornes (ill-shaped woman), Maritornes
Parabién (compliment), Parabienes
Vaivén (vibration), Vaivenes
The following are examples of the large class of nouns (compound) formed with a verb or adverb and a plural noun and which are used for both numbers—
Azotacalles (idler)
Buscavidas (pryer)
Cortaplumas (penknife)
Chupaflores (humming-bird)
Destripaterrones (navvy)
Lavamanos (wash-hand stand)
Limpiabotas (boot-black)
Matamoros (boaster)
Mondadientes (toothpick)
Papahueros (ninny)
Papamoscas (ninny)
Papanatas (ninny)
Paracaídas (parachute)
Paraguas (umbrella)
Pelagatos (ragamuffin)
Pintamonas (slap-dasher or bad partner)
Sacacorchos (corkscrew)
Salvavidas (life-boats)
Sepancuantos (slap or blow)