Some languages that grammaticalise for past tense do so by inflecting the verb, while others do so periphrastically using auxiliary verbs, also known as "verbal operators" (and some do both, as in the example of French given above). Not all languages grammaticalise verbs for past tense – Mandarin Chinese, for example, mainly uses lexical means (words like "yesterday" or "last week") to indicate that something took place in the past, although use can also be made of the tense/aspect markers "le" and "guo".