Rid

Do not confuse the verb 'to rid', which is pronounced to rhyme with 'did' (IPA: /dɪd/) with 'to ride', which rhymes with 'side' and 'hide' (IPA: /raɪd/). In particular, the past participle ridden belongs to ride, not here. The core meaning of 'to rid' is 'to clear away', or to 'disencumber', 'tidy up' etc. In current usage, OED's meaning 3. is probably predominant:

• a. To make (a person or place) free of (or from) something; to disencumber of.
• b. refl. To free or clear (oneself) of something troublesome. Now somewhat rare.
• c. to be rid of ([in obsolete use] on), to be freed from (a troublesome or useless thing or person).
• d. So to get rid of.

From c., we can see the grammatical analysis: rid in the phrase is a passive participle within a verb phrase using the be-passive. The phrase in d. is parallel in structure, using the informal get-passive. Consequently, students might take note that 'be rid of' is better suited to the careful formal variety of academic writing.

'To rid' is an irregular verb. Its forms are given here:

Base form	past tense	-ed participle	Remarks
rid	rid	rid	There is a variant ridded. AWE does not recommend it

This is one of the "the 250 or so irregular verbs" listed in Quirk 1985. The list "contains most of the irregular verbs in present-day English ... but is not meant to be exhaustive, particularly with regard to derivative verbs." AWE has copied most of the entries in that list. The verb 'to rid' belongs to Quirk's Class 5