Articles, Prepositions

1. What Articles Are (Determiners)

Articles = a, an, the — words before noun to indicate definiteness.

Indefinite a/an: non-specific ("a sensor" — any sensor). a before consonant sound (a university /j/, a one-way), an before vowel sound (an hour /aʊ/, an LED /el/, an umbrella).
Definite the: specific already known ("the sensor we installed").
Zero article: no article for general plural/uncountable ("Sensors are useful", "Water is needed").

Common error: "an universal" → a universal (since /j/ consonant), "a hour" → an hour.

2. What Prepositions Are

Preposition = word before noun/pronoun to show relation (place, time, direction, manner) + object = prepositional phrase (e.g., "in the lab", "on Monday").

Common prepositions: in, on, at, by, with, for, of, to, from, under, over, between, among.

Types: place (in, on, at, under), time (at 5pm, on Monday, in July, for 2 hours), direction (to, into, towards).

3. Why They Matter (technical writing)

Article error makes non-native writing non-fluent (e.g., "an sensor" → wrong).
Preposition error changes meaning: "in the system" vs "on the system".

4. Worked Examples

Articles: "a sensor, an actuator, the sensor (already mentioned), sensors in general (no article)."

Prepositions: "in the morning, on Monday, at 5pm" (time); "in the lab, on the table, at the door" (place); "by the sensor" (agent), "with a tool".

Correct: "a university, an hour, an honour, a one-time, an MBA". Choose by sound, not letter.

Error: "He is good in English" → "good **at** English" (collocation).

"The data is stored **in** the cloud **by** the server."

5. Exam Points

Distinguish a vs an with sound rule — 3-5 marks, frequent (often give 5 words to choose a/an).
Use the vs zero article — 3-5 marks, frequent.
Fill prepositions in blanks (in/on/at) — 5 marks, very frequent (common fill-in-the-blanks).
Correct article/preposition errors in sentence — 5 marks, frequent.

Articles, Prepositions