Examples:

(a) a roller coaster

(b) a ghost house

(c) a useful tool

(d) a university

Note: University is read as 'Yew-ni-ver-si-ty', thus it starts with a 'yew' sound not a 'u' sound. 

Examples:

(a) an elephant

(b) an unforgettable experience

(c) an orange

(d) an hour 

Note: Even though 'hour' starts with the letter 'h', which is a consonant, the word is read as A-WER. The 'h' sound is not pronounced.) 

1. The purse I lost was a present from my dad. (singular noun)
2. The cows in the field belong to Encik Dollah. (plural noun)

1. The earth orbits the sun at an average distance of 149.60 million km.
2. The moon is the earth's only natural satellite.

1. The Magic Funfair was in town once more. 
2. The Red Sea is the saltiest ocean in the world. 

Lions are wild animals.

(Meaning: all lions)

The lions are fed twice a day.

(Specific lions)

Brightly coloured flowers attract butterflies.

(Meaning: all flowers with bright colours attract butterflies)

The flowers in the vase are not real.

(Specific flowers)