до-

The prefix до- shifts the focus to the threshold of an action. At Level 5, it is important to distinguish its primary nuances:

• Completion to the End: Finishing an action completely. For example, дочитать means to read something to the end. These verbs are usually transitive, taking a direct object in the Accusative case (e.g., дочитать книгу).
• Spatial Boundary: Reaching a specific point in space. This is common with verbs of motion to emphasize the effort or the specific endpoint reached. This often uses the formula до- [verb] + до + [Genitive] (e.g., дойти до финиша).
• Temporal 'Until' Limit: Continuing an action until a specific time or event occurs, also using the до- [verb] + до + [Genitive] formula. For example, дожить до утра (to live until morning).
• Incremental Addition: Performing an action to reach a necessary standard or 'topping up.' These verbs typically take the Accusative or Partitive Genitive (e.g., долить воды [to top up with water], докупить продукты [to buy more groceries]).
• Extreme States and Negative Consequences: Reaching a state of exhaustion, negative consequences through persistent action, or finally achieving a difficult result. This often involves reflexive verbs (до- ... -ся), such as доиграться (to play until something bad happens) or дозвониться (to finally get through by phone). However, it also applies to transitive verbs used to bring someone or something else to a limit (e.g., довести кого-то до слёз [to bring someone to tears], довести до беды [to lead to disaster]). These verbs frequently pair with the до + [Genitive] formula to specify the extreme state or negative outcome reached (e.g., доиграться до слёз [to play or mess around until one cries], договориться до абсурда [to talk until it reaches absurdity]).
• 'Pre-' or 'Before' Adjectives: The prefix is highly productive in forming adjectives (and sometimes nouns) that mean 'pre-' or 'before' a certain event or period. Examples include довоенный (pre-war) and дошкольный (preschool).

Morphologically, adding до- to a base imperfective usually creates a perfective verb. These often form secondary imperfectives (like дочитывать) to describe the ongoing process of reaching the limit. For verbs of motion, adding the prefix to unidirectional verbs creates the perfective verb (e.g., идти → дойти), while adding it to multidirectional verbs creates its secondary imperfective counterpart (e.g., ходить → доходить). The prefix also attaches to adjectives or nouns to create adverbs indicating reaching an extreme state or physical limit (e.g., добела, досыта, допоздна). Phonetically, when до- is added to verbs, it is usually unstressed, though the stress can shift to the prefix in the past tense of certain verbs with monosyllabic roots (e.g., дожил, допил). In adverbs formed from adjectives or nouns, the stress often shifts to the prefix itself (e.g., досыта, досуха). It also forms the basis of the complex prefix недо-, which indicates that an action fell short of the required limit. Note the critical spelling and semantic difference between the solid prefix недо- (falling short of a norm, e.g., недосолить суп - to undersalt the soup) and the separate words не до- (not finishing an action, e.g., не досолить суп - to not finish salting the soup).