Expresses continuing an action without interruption. Attaches to volitional verb stems. The action is maintained deliberately or as an ongoing state. Distinct from 〜ている (which is neutral) — つづける emphasizes persistence. Also used with intransitive verbs to describe ongoing states.

Expresses proportional correlation — 'the more X, the more Y'. Multiple forms: V-ば V-ほど (すればするほど), イAdj-ければ イAdj-ほど (高ければ高いほど), NaAdj-なら NaAdj-なほど (静かなら静かなほど). 〜ほど alone can follow a single predicate. The second predicate often omits ば.

Expresses that a situation is steadily moving in one direction — typically worsening. Used for undesirable trends: 増える一方だ (only keeps increasing), 悪くなる一方だ (only getting worse), 下がる一方だ (only declining). The trend is monotonic and usually negative. Not used for improving situations.

Formal, often written expression for gradual, ongoing change or progress. Similar to 〜ている but more literary and emphasizes the process rather than the state. Often used with change-of-state verbs: 変わりつつある, 改善されつつある, 消えつつある. Not for instantaneous actions.

Expresses that something is just about to happen — the moment just before a change or action begins. Can describe natural phenomena (日が沈もうとしている), imminent events (会議が始まろうとしている), or someone's attempt (彼は成功しようとしている). The volitional form + とする literally means 'is trying to / is about to.'

Two distinct usages: (1) With V-辞書形: 'on the verge of, almost ready to' — 準備ができて、あとは出発するばかりだ (preparations done, just about to depart). (2) With V-た: 'just did' — identical to 〜たばかり (just did ~). Context distinguishes them. The V-辞書形 usage is formal/literary.

Expresses gradual, proportional change — as one thing changes, another changes along with it. Both clauses describe natural, often inevitable parallel changes. The change is continuous, not abrupt. Similar to 〜にしたがって but 〜につれて is more about natural accompaniment and less about following a rule or instruction.

Two main usages: (1) Proportional change — similar to につれて, as one thing changes, another follows (年を取るにしたがって). (2) Following a rule, instruction, or principle — 'in accordance with' (規則にしたがって, 指示にしたがって). In the progressive usage, したがって emphasizes following/correspondence more than the natural flow emphasized by につれて.

Multi-functional: (1) With N: 'together with' (家族とともに). (2) With V-辞書形: 'as, along with' progressive change (年を取るとともに). (3) 'At the same time as' — simultaneous occurrence (〜と同時に). The progressive usage (2) overlaps with 〜につれて and 〜にしたがって, but とともに is more neutral and less formal.

Expresses that a change in one thing brings about or accompanies a change in another. The connection is more causal than 〜につれて — one thing is driving the other. Often used for social, economic, or systemic changes. に伴う is the noun-modifying form. More formal and consequential than 〜とともに.