ごめん
「ごめん」 is a casual apology, used here before explaining why the plan must change. It is useful with friends or other people you speak to casually when you want to apologize briefly.
予定
「予定」 means the planned arrangement or appointment that is being changed here. A common reuse pattern is 「予定を」 followed by an action that affects the plan.
を
「を」 marks the direct object of the action in 「予定を変えないといけない」. It is placed after the thing that is changed, moved, or otherwise affected by an action.
変えない
「変えない」 means not change, but in 「変えないといけない」 the whole construction means that changing is necessary. It is the negative form of the citation form 変える, and this construction can be reused to say that an action must be done.
と
In 「変えないといけない」, 「と」 connects the required condition or content to the necessity expression. The meaning “must change” comes from the whole construction, not from 「と」 alone.
いけない
In 「変えないといけない」, 「いけない」 helps express that leaving the action undone is not acceptable, so the whole phrase means “must change.” The pattern plain-form action + 「といけない」 is a common way to express necessity.
んだ
「んだ」 gives a casual explanatory tone. Here it presents the need to change the plan as information being explained to the friend, and it is useful when giving background or a reason in casual conversation.
出かける
「出かける」 means to go out or leave, referring here to the action the friend was about to take. In 「出かける前に」, it is used before 前に to identify the event that has not happened yet.
前
「前」 means before in time here, specifically before leaving. In 「出かける前に」, it forms a common pattern meaning “before doing something.”
に
In 「出かける前に言ってくれて」, 「に」 marks the time when the telling happened relative to leaving. It commonly follows a time expression to show when an action takes place.
言って
「言って」 means saying or telling in 「言ってくれて」. It is the te-form of 言う and connects the telling action to the following expression, so the speaker can say they were glad to be told.
くれて
In 「言ってくれてよかった」, 「くれて」 shows that the other person’s telling was beneficial to the speaker. The whole expression conveys appreciation or relief, and the pattern verb-te + くれる can describe another person doing something for you.
よかった
「よかった」 means that something was good or fortunate here, expressing relief that the friend told the speaker before leaving. It is the past form of いい, and the pattern 「〜てよかった」 can say that it was good that something happened.
予想外
「予想外」 means unexpected or unforeseen, describing the event that caused the plan to change. It is used before の in 「予想外のこと」 to describe an unexpected event or matter.
の
In 「予想外のこと」, 「の」 links 「予想外」 to 「こと」 and lets the first noun describe the second. The reusable pattern noun + の + noun connects two nouns in this way.
こと
「こと」 means a thing, matter, or event here, referring to what happened unexpectedly. In 「予想外のこと」, it allows the speaker to refer broadly to an event without naming its specific details.
が
「が」 marks 「予想外のこと」 as the subject of 「起きた」, meaning that an unexpected thing occurred. It commonly follows the thing that happens or comes into existence.
起きた
「起きた」 means happened or occurred, referring to the unexpected event that has already happened. It is the past form of 起きる, and the pattern 「ことが起きた」 can report that an event occurred.
大丈夫
「大丈夫」 means all right or no problem, reassuring the friend that the change is acceptable. It is commonly used when accepting an apology or saying that a situation is okay.
だ
「だ」 makes the statement 「大丈夫だ」 plain and direct: the situation is okay. Here it states the assessment before 「よ」 adds a reassuring tone for the listener.
よ
「よ」 adds information or emphasis directed toward the listener. In 「大丈夫だよ」, it makes the reassurance sound like a clear message to the friend.
別
「別」 means another or different in 「別の日」, referring to a day other than the original one. It commonly comes before a noun when identifying an alternative.
日
「日」 means day or date here, the alternative day that the friends can choose. In 「別の日」, it identifies the time unit being selected.
選べる
「選べる」 means can choose, showing that the friends have the option of selecting another day. It is the potential form of 選ぶ and is used with the chosen item, as in 「別の日を選べる」.
今週
「今週」 means this week, the current week being discussed. It combines with a more specific time expression such as 「今週の後半」 to narrow down the proposed timing.
後半
「後半」 means the latter half or later part, referring here to the later part of this week. It is used after the period in 「今週の後半」.
なら
「なら」 marks the condition in 「今週の後半なら大丈夫」: if the time is later this week, it is okay. It can follow a noun or noun phrase when presenting a condition or choice.
で
In 「後半でいい」, 「で」 marks the proposed time as an acceptable arrangement or choice. The pattern time or option + 「でいい」 is useful for saying that a particular option is fine.
いい
「いい」 means okay, acceptable, or convenient here, saying that later this week works for the speaker. In 「後半でいい」, it accepts the proposed time as a suitable option.
新しい
「新しい」 means new, distinguishing the updated plan from the previous one. It comes directly before the noun in 「新しい予定」, a common adjective-before-noun pattern.
送れる
「送れる」 means can send, saying that the speaker is able to send the updated plan. It is the potential form of 送る and is used with the item being sent, as in 「新しい予定を送れる」.
それなら
「それなら」 means in that case or if that is the situation, responding to the offer to send the new plan. It is commonly used at the start of a reply when drawing a conclusion from what the other person just said.
調整
「調整」 means adjustment or coordination, referring here to adjusting the schedule. In 「予定を調整できる」, it combines with できる to express that the adjustment is possible.
できる
「できる」 means can or is possible; in 「調整できる」, it says that adjusting the schedule is possible. It commonly follows a noun such as 調整 to express that the activity can be done.