* One-way communication: While two-way communication is ideal, one person can communicate effectively using a language they understand, even if the other person doesn't. Think of a teacher explaining a concept to students who are still learning the language. The teacher understands the language fully, while the students are still developing their comprehension.
* Shared understanding: Communication isn't just about words, it's about conveying meaning. Even with limited language knowledge, people can use gestures, context, and shared experiences to communicate. Imagine two people who speak different languages trying to buy something in a shop. They might not speak each other's languages fluently, but they can use gestures and point to items to get their message across.
* Language evolution: Historically, new languages often developed from interactions between people who spoke different languages. This suggests that communication could occur even with incomplete understanding of each other's languages.
In conclusion: While two-way communication is ideal, it's not a strict requirement. Communication can be successful even with varying levels of language understanding, thanks to factors like context, shared experience, and creative use of non-verbal cues.