The Difference Between “Ago,” “Before,” “Formerly,” and “Previously”
English learners often confuse the words ago, before, formerly, and previously because they all relate to time. However, each has distinct meanings and usage rules. This guide will clarify their differences with explanations and examples.
1. Ago
Ago refers to a time in the past, measured from the present moment. It is always used with a time expression and follows it.
- Structure: [Time Expression] + ago
- Example: “She left two hours ago.” (Meaning: She left two hours before now.)
- Note: “Ago” cannot be used with past perfect tense.
2. Before
Before is more flexible and can refer to:
- Earlier than a specific time/event: “He arrived before the meeting started.”
- In the past generally: “I’ve seen this movie before.”
- As a conjunction: “Call me before you leave.”
Key difference from “ago”: “Before” does not require a time expression and can refer to any past time, not necessarily from the present.
3. Formerly
Formerly means “in the past, but not anymore.” It emphasizes a change in state or identity.
- Example: “This building was formerly a school.” (It is no longer a school.)
- Common usage: Often used for names, titles, or roles (e.g., “Formerly known as…”).
4. Previously
Previously means “at an earlier time” and is often used to refer to something mentioned earlier or a prior state.
- Example: “As mentioned previously, the event starts at 8 PM.”
- Difference from “formerly”: “Previously” does not necessarily imply a change—just that something happened earlier.
Comparison Table
| Word | Meaning | Usage | Example |
|---|---|---|---|
| Ago | Past time from now | Follows a time expression | “He called 10 minutes ago.” |
| Before | Earlier than a time/event | Flexible (standalone or with reference) | “Finish your work before 5 PM.” |
| Formerly | No longer the case | Emphasizes change | “She was formerly a lawyer.” |
| Previously | At an earlier time | Refers to prior events/states | “Previously, we discussed this issue.” |
Common Mistakes to Avoid
- Incorrect: “I saw her ago.” (Missing time expression.)
- Correct: “I saw her a week ago.”
- Incorrect: “He worked here formerly.” (If he still does, use “previously.”)
- Correct: “He formerly worked here (but now he doesn’t).”
Practice Examples
Fill in the blanks with ago, before, formerly, or previously:
- She moved to London ___ known as Smith.
- We met ___ at a conference.
- The train departed ___ 10 minutes.
- ___ you go, check your email.
Answers: 1. formerly, 2. previously, 3. ago, 4. before