1
A metaphor is a figure of speech that compares two unlike things without using 'like' or 'as'.
翻译
隐喻是一种修辞手法，通过不借助'像'或'作为'等比较词，将两个本质不同的事物进行类比。
重点解析：本句定义解释句以'is'为系动词，后接表语从句'That compares two unlike things without using 'like' or 'as''。其中'that'引导的定语从句修饰'figure of speech'，'compares'为动词原形，'two unlike things'为比较对象，'without using'为介词'without'引导的状语，表示否定方式。整个句子的核心结构是'主系表'，表语从句中包含宾语从句结构。
2
Photosynthesis is the process by which green plants use sunlight to synthesize nutrients from carbon dioxide and water.
翻译
光合作用是指绿色植物利用阳光，将二氧化碳和水转化为养分的生化过程。
重点解析：这是一个典型的定义句，'is'作为系动词，后接表语从句'by which green plants use sunlight to synthesize nutrients from carbon dioxide and water'。'by which'是关系副词，引导定语从句修饰'process'。'use'是动词原形，'to synthesize'是不定式作目的状语，'from carbon dioxide and water'是介词短语作来源状语。
3
A polygon is a closed plane figure with at least three straight sides and angles.
翻译
多边形是指由至少三条直线边和角构成的封闭平面图形。
重点解析：本句定义句以'is'为系动词，后接表语'closed plane figure'。'with at least three straight sides and angles'是介词短语作后置定语，修饰'figure'。'at least'表示最低限度，'straight'是形容词修饰'sides'，'angles'是复数名词，表示多边形的角。
4
Gravity is the force that attracts a body toward the center of the earth or toward any other physical body having mass.
翻译
重力是指使物体向地球中心或任何其他具有质量的物体移动的引力。
重点解析：这是一个定义句，'is'为系动词，'the force'为表语。'that'引导的定语从句修饰'force'，'attracts'是动词，'a body'是宾语，'toward the center of the earth'和'toward any other physical body having mass'是介词短语作状语，表示方向。'having mass'是现在分词短语作后置定语修饰'body'。
5
An ecosystem is a community of living organisms in conjunction with the nonliving components of their environment, interacting as a system.
翻译
生态系统是指与其环境中的非生物成分相互作用的生物群落，作为一个整体系统。
重点解析：本句定义句以'is'为系动词，'a community'为表语。'of living organisms'是介词短语作后置定语修饰'community'，'in conjunction with the nonliving components of their environment'是介词短语作伴随状语，'interacting as a system'是现在分词短语作结果状语。
6
A hypothesis is an educated guess that can be tested by observation or experimentation.
翻译
假设是指可以通过观察或实验进行验证的有根据的推测。
重点解析：这是一个定义句，'is'为系动词，'an educated guess'为表语。'that'引导的定语从句修饰'guess'，'can be tested'是情态动词+被动语态结构，'by observation or experimentation'是介词短语作方式状语。
7
A biography is a detailed description or account of someone's life written by another person.
翻译
传记是指由他人撰写的关于某人生活经历的详细记述。
重点解析：本句定义句以'is'为系动词，'a detailed description or account'为表语。'of someone's life'是介词短语作后置定语修饰'description'，'written by another person'是过去分词短语作后置定语修饰'biography'。
8
A paradox is a statement that appears to be self-contradictory or silly but may include a latent truth.
翻译
悖论是指看似自相矛盾或荒谬，但可能蕴含潜在真理的陈述。
重点解析：这是一个定义句，'is'为系动词，'a statement'为表语。'that'引导的定语从句修饰'statement'，'appears to be'是动词短语，'self-contradictory or silly'是形容词短语作表语补足语，'but may include'是并列连词引导的并列分句，'a latent truth'是宾语。
9
An analogy is a comparison between two things, typically for the purpose of explanation or clarification.
翻译
类比是指两种事物之间的比较，通常用于解释或澄清。
重点解析：本句定义句以'is'为系动词，'a comparison'为表语。'between two things'是介词短语作后置定语修饰'comparison'，'typically for the purpose of explanation or clarification'是介词短语作目的状语。
10
A narrative is a story that describes a series of fictional or non-fictional events.
翻译
叙述是指描述一系列虚构或非虚构事件的故事。
重点解析：这是一个定义句，'is'为系动词，'a story'为表语。'that'引导的定语从句修饰'story'，'describes'是动词，'a series of fictional or non-fictional events'是宾语。
11
A compound is a substance formed when two or more chemical elements are chemically bonded together.
翻译
化合物是指两个或更多化学元素通过化学键结合形成的物质。
重点解析：本句定义句以'is'为系动词，'a substance'为表语。'formed when two or more chemical elements are chemically bonded together'是过去分词短语作后置定语修饰'substance'，'when'引导时间状语从句，'are bonded'是被动语态结构。
12
A metaphor is a figure of speech that compares two unlike things without using 'like' or 'as'.
翻译
隐喻是一种修辞手法，通过不借助'像'或'作为'等比较词，将两个本质不同的事物进行类比。
重点解析：这是一个重复的例句，用于强调定义句的常见结构。'is'为系动词，'a figure of speech'为表语。'that'引导的定语从句修饰'figure of speech'，'compares'是动词原形，'two unlike things'是宾语，'without using'是介词短语作方式状语，表示否定方式。