asma (the bogie-man)
El frente (the front) La frente (the forehead)
El haz (the sheaf) La haz (face, surface)
Lente (lenses), doubtful gender
La orden (command, order for El orden (order); as, buen orden
goods, etc.) (good order)
Las sagradas ordenes (holy orders) Las varias ordenes (various religious
orders)
El parte (report) La parte (part)
El pendiente (ear-ring) La pendiente (slope)
El pez (fish) La pez (pitch)
El tema (exercise, theme) La tema (fear, obstinacy)
Tilde (~), doubtful gender

"Mar" (sea) is either Masc. or fem., but names of particular seas are
all masculine--

El mar rojo (the Red Sea)
El mar Caspio (the Caspian Sea)

The compounds of "mar" are feminine--

Baja mar (low sea)
Pleamar (high water)

The following masculine nouns have their equivalent feminine formed by
inflexion.

N.B.--We omit those in which the inflexion consists of the change of the
last vowel to _a_, or the addition of _a_, as--

El autor, la autora (the author, authoress)
El holgazan, la holgazana (the lazy man, lazy woman)
El primo, la prima (the cousin, _masc._ and _fem._)
El vecino, la vecina (the neighbour, _masc._ and _fem._)

El abad (abbot) La abadesa (abbess)
El actor (actor) La actriz (actress)
El baron (baron) La baronesa (baroness)
El canonigo (canon) La canonesa (canoness)
El cantor (singer) La cantatriz (singer)
El conde (count) La condesa (countess)
El diacono (deacon) La diaconisa (deaconess)
El duque (duke) La duquesa (duchess)
El elector (elector) La electriz (electress)
El emperador (emperor) La emperatriz (empress)
El filosofo (philosopher) La filosofesa (philosopher)
El gallo (cock) La gallina (hen)
El heroe (hero) La heroina (heroine)
El poeta (poet) La poetisa (poetess)
El principe (prince) La princesa (princess)
El profeta (prophet) La profetisa (prophetess)
El rey (king) La reina (queen)
El sacerdote (priest) La sacerdotisa (priestess)
El vizconde (viscount) La vizcondesa (viscountess)
El Zar (czar) La Zarina (czarina)

Notice also--

El asistente (assistant) La asistenta (assis