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"La tuya" is a form of "tuya", an adjective which is often translated as "yours". "Suya" is a form of "suya", an adjective which is often translated as "his". Learn more about the difference between "la tuya" and "suya" below.
tuya(
too
-
yah
)An adjective is a word that describes a noun (e.g., the big dog).
1. (informal) (possessive; second person singular)
A word or phrase used to refer to the second person informal “tú” by their conjugation or implied context (e.g., How are you?).
A pronoun is a word that stands in for a noun (e.g., she).
2. (informal) (possessive; second person singular)
A word or phrase used to refer to the second person informal “tú” by their conjugation or implied context (e.g., How are you?).
a. yours 
Me robaron la bicicleta. ¿Puedo utilizar la tuya esta semana?My bicycle was stolen. Can I use yours this week?
A feminine noun is almost always used with feminine articles and adjectives (e.g., la mujer bonita, la luna llena).
3. (botany)
a. white cedar 
Yo elegiría una madera sólida para la cerca, por ejemplo, tuya o pino.For the fence, I would choose solid wood like white cedar or pine.
suya(
soo
-
yah
)An adjective is a word that describes a noun (e.g., the big dog).
a. his  (masculine) (singular)
A word or phrase that is masculine (e.g., el libro).
A word or phrase that is singular (e.g., el gato).
Mi botella es azul mientras la botella suya es morada.My bottle is blue whereas his bottle is purple.
b. her  (feminine) (singular)
A word or phrase that is feminine (e.g., la manzana).
A word or phrase that is singular (e.g., el gato).
¿Conoces a Laura? Esta mansión es suya.Do you know Laura? This is her mansion.
c. its  (singular)
A word or phrase that is singular (e.g., el gato).
¿Hay perro? - Parece que sí; esa debe de ser la caseta suya.Is there a dog? - It looks like it. That must be its kennel.
2. (formal) (possessive; second person singular)
A word or phrase used to refer to the second person formal “usted” by their conjugation or implied context (e.g., usted).
a. your 
Ya voy a su casa. ¿Cuál es la dirección suya?I'm on my way to your house. What is your address?
A pronoun is a word that stands in for a noun (e.g., she).
a. his  (masculine) (singular)
A word or phrase that is masculine (e.g., el libro).
A word or phrase that is singular (e.g., el gato).
¿Esa es la camioneta de Federico? - No, la suya es negra.Is that Federico's truck? - No, his is black.
b. hers  (feminine) (singular)
A word or phrase that is feminine (e.g., la manzana).
A word or phrase that is singular (e.g., el gato).
Me olvidé de traer mi computadora. - No te preocupes. Ana trajo la suya.I forgot to bring my computer. - Don't worry. Ana brought hers.
5. (formal) (possessive; second person singular)
A word or phrase used to refer to the second person formal “usted” by their conjugation or implied context (e.g., usted).
a. yours 
Señor, mi pluma se quedó sin tinta. ¿Puedo usar la suya?Sir, my pen is out of ink. Can I use yours?
a. yours 
Estas son nuestras llaves. Las suyas son más pequeñas.These are our keys. Yours are smaller.