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4 Tools and methods for designing lightweight parts Lightweight design always has been a hot topic in structural engineering .
 machine or equipment: Tools; concept or principle: lightweight; concept or principle: Lightweight; engineering feature: design; concept or principle: structural engineering
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: manufacturing standard, machanical property, manufacturing process, material, engineering feature, process parameter, machine or equipment, application, process characterization, enabling technology, biomedical, concept or principle 
Text: {0} 
 Entities: Tools, lightweight, Lightweight, design, structural engineering 
Answer:
 machine or equipment: Tools; concept or principle: lightweight; concept or principle: Lightweight; engineering feature: design; concept or principle: structural engineering