Understanding English Grammar: Identifying the Problem in the Sentence

The original sentence is: "As we’ve been neighbours, I have known Mrs. Shashi Singh since more than 16 years."

The underlined part "since more than 16 years" is where the potential grammar issue lies. We need to determine if the word "since" is used correctly in this context, particularly with the verb tense and the time phrase "more than 16 years".

Analyzing the Verb Tense: Present Perfect

The verb used in the main clause is "have known", which is in the present perfect tense. The present perfect tense is used to describe an action or state that began in the past and continues up to the present moment, or a past action that has relevance in the present.

Grammar Rules: Using 'For' and 'Since' with Present Perfect

When using the present perfect tense to indicate duration (how long something has been happening), we typically use:

• For: Used with a period or duration of time (e.g., for two hours, for a week, for many years, for more than 16 years). It answers the question "How long?"
• Since: Used with a specific point in time in the past when the action started (e.g., since Monday, since 2010, since I was a child, since she left). It answers the question "Since when?"

Evaluating the Underlined Phrase: Duration or Point in Time?

The phrase "more than 16 years" refers to a length of time, a duration. It tells us how long the speaker has known Mrs. Shashi Singh. According to the grammar rule, when talking about a duration with the present perfect tense, we should use "for".

Using "since" with a duration like "more than 16 years" is grammatically incorrect in standard English.

Examining the Options for Sentence Improvement

Let's look at the provided options to see which one correctly replaces the underlined part "since more than 16 years".

• Option 1: by more than 16 years

  The word "by" is usually used to indicate a deadline (e.g., by tomorrow) or a margin of difference (e.g., taller by an inch). It is not used to indicate a duration with the present perfect tense.

• Option 2: from more than 16 years

  "From" can indicate a starting point, but it's not the standard word used with a duration in the present perfect. For example, you might say "from now on" or "from 2010 onwards", but not typically "I have known her from more than 16 years" to express the length of time.

• Option 3: No improvement

  As established earlier, using "since" with a duration ("more than 16 years") is grammatically incorrect. Therefore, the sentence does require improvement.

• Option 4: for more than 16 years

  The word "for" is used correctly here with the duration "more than 16 years" and the present perfect tense "have known". This correctly expresses the length of time the speaker has known Mrs. Shashi Singh.

Conclusion: Selecting the Correct Improvement for the Sentence

Based on the rules for using "for" and "since" with the present perfect tense, the phrase "more than 16 years" represents a duration. The correct preposition to use with a duration in this context is "for". Therefore, the phrase should be "for more than 16 years".

The option that provides this correct phrasing is Option 4.

Revision Table: For vs. Since with Present Perfect

Additional Information: Present Perfect and Time Expressions

The present perfect tense can be used with various time expressions. While "for" and "since" are common for indicating duration or starting points, other expressions can also be used, such as "already", "yet", "just", "ever", and "never".

It's important to distinguish between a duration (a period of time) and a specific point in time when choosing between "for" and "since" when discussing how long an action has been ongoing up to the present.