QUICK ANSWER
"Relámpagos" is a form of "relámpago", a noun which is often translated as "bolt of lightning". "Hay truenos" is a phrase which is often translated as "there's thunder". Learn more about the difference between "relámpagos" and "hay truenos" below.
el relámpago(
rreh
-
lahm
-
pah
-
goh
)A masculine noun is used with masculine articles and adjectives (e.g., el hombre guapo, el sol amarillo).
1. (weather)
a. bolt of lightning
Un relámpago iluminó el cielo entero.A bolt of lightning lit up the whole sky.
Zeus lanzó un relámpago hacia la Tierra.Zeus hurled a bolt of lightning toward Earth.
b. lightning (uncountable)
Hubo muchos relámpagos anoche durante la tormenta.There was a lot of lightning last night during the storm.
c. lightning bolt
El gatito se escondió debajo de las escaleras después de ver el relámpago.The kitty hid under the stairs after seeing the lightning bolt.
hay truenos
A phrase is a group of words commonly used together (e.g., once upon a time).
1. (general)
a. there's thunder
Está diluviando, y hay truenos y relámpagos.It's pouring with rain, and there's thunder and lightning.
b. there are thunderclaps
A mí me dan mucho miedo las tormentas, sobre todo cuando hay truenos.I'm very frightened of storms, especially when there are thunderclaps.
c. there are claps of thunder
El héroe despierta en medio de una tormenta: hay truenos, y un relámpago ilumina el cielo de vez en cuando.The hero wakes up in the middle of a storm: there are claps of thunder, and a flash of lightning illuminates the sky now and then.
