Mastering English Time Prepositions: For, Since, and Ago

In the English language, prepositions related to time are essential for clear communication, yet they are frequently misused by learners. Emma from mmmEnglish provides a comprehensive guide on distinguishing between "for," "since," and "ago," highlighting how each serves a specific function in describing when and how long actions occur.

Using 'Ago' for Completed Past Actions

"Ago" acts as a preposition of time used to indicate how far back in the past an event took place relative to the present. Emma emphasizes that "ago" is always used with an "amount of time" (e.g., "ten years ago," "three days ago") and consistently appears at the end of a sentence or clause.

Crucially, "ago" is tethered to the past simple tense. It describes "completed actions in the past" and pinpointing exactly when they happened. For example, stating "She moved to Sydney ten years ago" identifies the specific moment in the past (2013) when the event occurred.

Using 'For' to Express Duration

While "ago" marks a point in time, "for" is used to define a "length of time or a period of time." It precedes the duration of an action, such as "for two minutes" or "for a long time." Unlike "ago," "for" is highly versatile; it is frequently paired with "perfect tenses" to describe actions that "started in the past and continues up until the present," but it can also be used in other tenses, such as "we'll be away for seven days" or "we spoke for one minute."

Emma notes that the primary purpose of "for" is to emphasize the "duration" of an event rather than the start date. If someone asks, "How long has Sarah lived in Sydney?" replying "She's lived in Sydney for ten years" highlights the total span of her residency.

Using 'Since' for Starting Points

"Since" serves a distinct role by focusing on the "precise moment that an action or a state began." Unlike "for," which looks at the total duration, "since" points to a specific day, date, or time (e.g., "since 2013," "since the start of June"). Because "since" describes an action that has been "in progress" from a starting point up until now, it is almost exclusively used with "perfect verb tenses."

Emma provides a comparative example to clarify the nuance:

• "I've worked here for two months" (focuses on duration).
• "I've worked here since the start of June" (focuses on the starting point).

Summary of Key Differences

To summarize, the choice between these three depends on the speaker's intent:

• Ago: Used with the past simple to show how far back a completed action occurred.
• For: Used to express the total duration of an event, regardless of the tense, though common in perfect tenses.
• Since: Used with perfect tenses to pinpoint the exact moment an action or state commenced.

Mastering these nuances allows for more precise storytelling and reporting of events in English. By paying attention to whether you are highlighting a completed past moment, a total duration, or a specific starting point, you can select the correct preposition with confidence.