được + Duration

To express the achieved or accumulated duration of an action, use the structure:

[Subject] + [Verb] + (Object/Location) + được + [Duration]

• The Nuance: Because được implies obtaining or achieving, this pattern carries the subtle feeling of having successfully accumulated a specific amount of time doing an action. By itself, this structure only expresses achieved duration, which could be entirely in the past. Note that because được implies achieving time, you must use mất or tốn instead when talking about time that is 'spent', 'consumed', or 'lost' to complete a task (e.g., 'It took me 3 hours to fix the car').
• được vs. trong: English speakers often try to use trong (in/during) to mean 'for' a duration. However, trong 2 năm simply describes a static block of time ('during a 2-year period') or is used for future or allotted time (e.g., Tôi sẽ học trong 2 tiếng). To express that time has been accumulated or achieved up to a certain point ('for 2 years so far'), you typically use được, though it is frequently omitted in everyday speech if rồi is used at the end of the sentence to anchor the time.
• Anchoring the Timeframe: To show that the duration has reached a certain point, it is extremely common to add Already or nay (this/now) at the end of the sentence. Note that rồi simply means 'already' and anchors the duration to the context's timeframe (which could be in the past), whereas nay strictly anchors the action to right now (e.g., được hai năm rồi vs. được hai năm nay).
• Word Order: As a general rule, place the được + [Duration] block at the very end of the clause, after the object or location (e.g., Tôi học tiếng Việt được 2 năm rồi). You can also place the duration before the object (e.g., Tôi học được 2 năm tiếng Việt rồi). In this position, the duration acts as a quantifier modifying the noun (literally: '2 years of Vietnamese'), so this alternative word order only works with generic nouns or activities. It does not work with specific, definite objects (e.g., you cannot say Tôi quen được 2 năm anh ấy rồi).
• Ongoing vs. Completed: Adding rồi can sometimes be ambiguous about whether the action is still ongoing or has finished (e.g., Tôi sống ở đây được 2 năm rồi could mean you still live there or you are moving away). Context usually makes it clear, but you can add words like vẫn đang to clarify that the action is strictly ongoing.
• Negative Sentences: When expressing that you haven't done something for a certain duration (e.g., 'I haven't seen him for 2 years'), use the structure: [Subject] + không + [Verb] + (Object) + (được) + [Duration] + rồi. In these cases, được is frequently omitted, though keeping it is also perfectly correct to emphasize the length of time (e.g., Tôi không gặp anh ấy (được) 2 năm rồi).
• Past tense marker: You can use the past marker Completed Action to emphasize that the action started in the past (e.g., Tôi đã học tiếng Việt được 2 năm rồi). While được inherently signals that the accumulation of time began in the past, making đã optional, it is still frequently used.
• Asking 'How Long': To ask a question, simply replace the duration with How Long (e.g., ...được bao lâu rồi?).
• Ambiguity with Ability: Note that the pattern [Verb] + được + [Duration] can sometimes be ambiguous with the ability meaning of được (see Can (managed to)). For example, Tôi ngủ được 2 tiếng could mean 'I slept for 2 hours' (duration) or 'I was able to sleep for 2 hours' (ability). Context usually makes this clear, and adding rồi at the end strongly points to the duration meaning. Furthermore, if you place được before the verb, it changes the meaning to Passive For Something Welcome or May / Be Allowed To.